fix: add exponential backoff

[PertsevRoman]

I faced with DNS/timeout issues during agent initialization
WebSocket mode

io.jenkins.remoting.shaded.javax.websocket.DeploymentException: Connection failed.
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.JdkClientContainer$1.call(JdkClientContainer.java:187)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.JdkClientContainer$1.call(JdkClientContainer.java:107)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.JdkClientContainer.openClientSocket(JdkClientContainer.java:192)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.client.ClientManager$3$1.run(ClientManager.java:647)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.client.ClientManager$3.run(ClientManager.java:696)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.client.ClientManager$SameThreadExecutorService.execute(ClientManager.java:849)
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:112)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.client.ClientManager.connectToServer(ClientManager.java:493)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.client.ClientManager.connectToServer(ClientManager.java:337)
	at hudson.remoting.Engine.runWebSocket(Engine.java:656)
	at hudson.remoting.Engine.run(Engine.java:495)
Caused by: java.nio.channels.UnresolvedAddressException
	at sun.nio.ch.Net.checkAddress(Net.java:104)
	at sun.nio.ch.UnixAsynchronousSocketChannelImpl.implConnect(UnixAsynchronousSocketChannelImpl.java:302)
	at sun.nio.ch.AsynchronousSocketChannelImpl.connect(AsynchronousSocketChannelImpl.java:210)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.TransportFilter.handleConnect(TransportFilter.java:184)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.Filter.connect(Filter.java:80)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.Filter.connect(Filter.java:83)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.Filter.connect(Filter.java:83)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.ClientFilter.connect(ClientFilter.java:99)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.JdkClientContainer.connectSynchronously(JdkClientContainer.java:326)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.JdkClientContainer.access$700(JdkClientContainer.java:58)
	at io.jenkins.remoting.shaded.org.glassfish.tyrus.container.jdk.client.JdkClientContainer$1.call(JdkClientContainer.java:156)
	... 12 more

TCP socket mode

java.io.IOException: Failed to connect to http://jenkins-url/tcpSlaveAgentListener/: connect timed out
	at org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver.resolve(JnlpAgentEndpointResolver.java:214)
	at hudson.remoting.Engine.innerRun(Engine.java:733)
	at hudson.remoting.Engine.run(Engine.java:539)
Caused by: java.net.SocketTimeoutException: connect timed out
	at java.net.PlainSocketImpl.socketConnect(Native Method)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:607)
	at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
	at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
	at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
	at sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
	at sun.net.www.http.HttpClient.New(HttpClient.java:339)
	at sun.net.www.http.HttpClient.New(HttpClient.java:357)
	at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1228)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1162)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
	at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:990)
	at org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver.resolve(JnlpAgentEndpointResolver.java:211)
	... 2 more

I'm trying to detect exact issue. Seems it relates to some K8s/JDK networking corner case.
Anyway the PR introduces exponential backoff workaround which resolves the issue on source code level. It can help to avoid potential network issues.

[jeffret-b]

The idea seems fine. Exponential backoff can be useful. In this case, we need an associated Jira ticket that sufficiently describes the problem and some indication that this resolves or improves the situation.

[jeffret-b]

Please don't combine imports. They should be one per line.

Also, it would be nice if the reformatting were separated. At least in a separate commit. Maybe a separate PR.

[jeffret-b]

Generally we don't like to add dependencies to Remoting, but this one is small, so it's probably okay.

[jglick]

Though do we really need a third-party dependency for exponential backoff? Remoting already retries connection, and typically you need to tune backoff behavior a bit for the caller anyway. E.g. https://github.com/jenkinsci/apache-httpcomponents-client-4-api-plugin/blob/4e7d9a7bae61f816f95f6fc1fb144e6ed40895f1/src/main/java/io/jenkins/plugins/httpclient/RobustHTTPClient.java#L159-L216

[jeffret-b]

Any reason not to use primitives?

[jglick]

Merge conflict, possibly with #603 etc. The idea is fine but this is probably a candidate for closing unless the author still has time and interest in cleaning it up.

[jglick]

Probably superseded by #676.