feat(instrumentation): add getModuleDefinitions() instead of making init() public

[pichlermarc]

Which problem is this PR solving?

Reviewing all changes for the next release, I've just realized that the changes from #4418 would be breaking for implementations that add the protected keyword to init(), which turns out to be a lot of them in contrib. This is my proposal, adding a new method that should have the same effect, but won't require changes to instrumentations.

cc @drewcorlin1, I think this would also work, right?
cc @dyladan since you also reviewed #4418

Relates to #4418

Short description of the changes

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Exisitng unit tests
• Added unit tests

[codecov]

Codecov Report

Merging #4475 (7168e3d) into main (44b0b29) will decrease coverage by 0.13%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4475      +/-   ##
==========================================
- Coverage   92.55%   92.43%   -0.13%     
==========================================
  Files         315      330      +15     
  Lines        9375     9525     +150     
  Branches     2013     2033      +20     
==========================================
+ Hits         8677     8804     +127     
- Misses        698      721      +23     

Files	Coverage Δ
...entelemetry-instrumentation/src/instrumentation.ts	80.48% <100.00%> (+2.71%)	⬆️

... and 16 files with indirect coverage changes

[drewcorlin1]

@pichlermarc yes this should also work! thank you!

[drewcorlin1]

@pichlermarc yes this should also work! thank you!

I'll also get back to the esbuild MR once this has been merged, just been waiting to use this without all the @ts-ignore's in that 😄