gRPC Swift 1.12.0

SemVer Minor

• Make GRPCAsyncRequestStreamWriter.finish() sync and non-throwing (#1504, patch credit to @schwmi)
• Allow writing a sequence of requests/responses (#1499)

SemVer Patch

• Log TLS version (#1509)
• Fix sendable warnings (#1513)
• Bump version number to 1.12.0 (#1516)

Other Changes

• Remove invalid command line args from the example (#1496, patch credit to @lkstc112233)
• Fix HelloWorld examples (#1505, #1512)