Adjust Lucene version and enable BWC tests (elastic#77933)

This commit adjust Lucene version in 7x after it was upgraded to Lucene 8.10.

Relates elastic#77801
Relates elastic#77898

build.gradle

@@ -140,9 +140,9 @@ tasks.register("verifyVersions") {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
+boolean bwc_tests_enabled = true
 // place a PR link here when committing bwc changes:
-String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/77898"
+String bwc_tests_disabled_issue = ""
 /*
  * FIPS 140-2 behavior was fixed in 7.11.0. Before that there is no way to run elasticsearch in a
  * JVM that is properly configured to be in fips mode with BCFIPS. For now we need to disable

server/src/main/java/org/elasticsearch/Version.java

@@ -89,7 +89,7 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_7_14_1 = new Version(7140199, org.apache.lucene.util.Version.LUCENE_8_9_0);
     public static final Version V_7_14_2 = new Version(7140299, org.apache.lucene.util.Version.LUCENE_8_9_0);
     public static final Version V_7_15_0 = new Version(7150099, org.apache.lucene.util.Version.LUCENE_8_9_0);
-    public static final Version V_7_16_0 = new Version(7160099, org.apache.lucene.util.Version.LUCENE_8_9_0);
+    public static final Version V_7_16_0 = new Version(7160099, org.apache.lucene.util.Version.LUCENE_8_10_0);
     public static final Version V_8_0_0 = new Version(8000099, org.apache.lucene.util.Version.LUCENE_8_10_0);
     public static final Version CURRENT = V_8_0_0;