Adjust testGetSslCertificates to run in FIPS (#40046)

As discovered in #40041, when parsing certificates from files, the
SUN Security Provider normalizes DNs from parsed certificates by
adding spaces between RDNs, while the BouncyCastle one (which we
use in FIPS tests) does not.

We could proceed to normalize the DNs in the same manner in this
test by using i.e. the Unbound LDAP SDK but since the goal of this
test is to validate that we do get to read these exact certificates
from our trust sources and not to validate subject DNs, this commit
changes the test to check the serial number instead

Resolves: #40041

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/SecurityDocumentationIT.java

@@ -964,7 +964,6 @@ public void onFailure(Exception e) {
     }
 
     public void testGetSslCertificates() throws Exception {
-        assumeFalse("Awaits fix: https://github.com/elastic/elasticsearch/issues/40041", inFipsJvm());
         RestHighLevelClient client = highLevelClient();
         {
             //tag::get-certificates-execute
@@ -980,39 +979,39 @@ public void testGetSslCertificates() throws Exception {
             assertThat(certificates.size(), Matchers.equalTo(9));
             final Iterator<CertificateInfo> it = certificates.iterator();
             CertificateInfo c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=testnode-client-profile"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("c0ea4216e8ff0fd8"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=Elasticsearch Test Node, OU=elasticsearch, O=org"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("b8b96c37e332cccb"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.crt"));
             assertThat(c.getFormat(), Matchers.equalTo("PEM"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=OpenLDAP, OU=Elasticsearch, O=Elastic, L=Mountain View, ST=CA, C=US"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("d3850b2b1995ad5f"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=Elasticsearch Test Node, OU=elasticsearch, O=org"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("b8b96c37e332cccb"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=Elasticsearch Test Client, OU=elasticsearch, O=org"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("b9d497f2924bbe29"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=ad-ELASTICSEARCHAD-CA, DC=ad, DC=test, DC=elasticsearch, DC=com"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("580db8ad52bb168a4080e1df122a3f56"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=Elasticsearch Test Node"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("7268203b"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=samba4"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("3151a81eec8d4e34c56a8466a8510bcfbe63cc31"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
             c = it.next();
-            assertThat(c.getSubjectDn(), Matchers.equalTo("CN=Elasticsearch Test Node"));
+            assertThat(c.getSerialNumber(), Matchers.equalTo("223c736a"));
             assertThat(c.getPath(), Matchers.equalTo("testnode.jks"));
             assertThat(c.getFormat(), Matchers.equalTo("jks"));
         }