Java 21 compatibility

[meiao]

Overview

Changes to make sure that the agent works with Java 21.

• all tests that ran with Java 20 now run with 21;
• new instrumentation module due to changes in java.net.Socket;
• adapting instrumentation due to change in lambda's .toString().

Related Github Issue

Resolves #1498

Checks

• Your contributions are backwards compatible with relevant frameworks and APIs.
• Your code does not contain any breaking changes. Otherwise please describe.
• Your code does not introduce any new dependencies. Otherwise please describe.

[jbedell-newrelic]

We should create a ticket to remind us to turn the Log4J1 tests back on when 21.0.1 is released.

[codecov-commenter]

Codecov Report

Merging #1546 (f747237) into main (0e70cdf) will increase coverage by 0.04%.
Report is 46 commits behind head on main.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #1546      +/-   ##
============================================
+ Coverage     70.58%   70.63%   +0.04%     
- Complexity     9754     9782      +28     
============================================
  Files           814      816       +2     
  Lines         39300    39419     +119     
  Branches       5967     5978      +11     
============================================
+ Hits          27739    27842     +103     
- Misses         8870     8879       +9     
- Partials       2691     2698       +7     

Files	Coverage Δ
...va/com/newrelic/agent/config/JavaVersionUtils.java	91.30% <100.00%> (ø)

... and 15 files with indirect coverage changes

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[meiao]

Ticket to reenable the tests
#1547