Add Gradle toolchain support so -PtestJavaVersion will automatically download Java version

[trask]

This is same as instrumentation repo uses.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.09%. Comparing base (567e737) to head (f1a452f).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7680      +/-   ##
============================================
- Coverage     90.12%   90.09%   -0.03%     
+ Complexity     7183     7181       -2     
============================================
  Files           814      814              
  Lines         21675    21675              
  Branches       2123     2123              
============================================
- Hits          19534    19529       -5     
- Misses         1475     1478       +3     
- Partials        666      668       +2     

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