feat(opencensus-shim) add require-in-the-middle hook to patch @opencensus/core

[aabmass]

Which problem is this PR solving?

Part of #3749 [4 of 5]. Final state of the series of PRs: #3778

Short description of the changes

Adds a require-in-the-middle hook to patch @opencensus/core to return a ShimTracers. Includes a register script that can be used like node -r @opentelemetry/shim-opencensus/register ... to automatically install the hook at startup.

Type of change

Please delete options that are not relevant.

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

How Has This Been Tested?

Added tests in this PR. I also have an example in the next PR which I tested out to be working.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #3809 (2902f05) into main (a8ac8ba) will decrease coverage by 0.02%.
The diff coverage is 93.33%.

❗ Current head 2902f05 differs from pull request most recent head cf27880. Consider uploading reports for the commit cf27880 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3809      +/-   ##
==========================================
- Coverage   92.95%   92.94%   -0.02%     
==========================================
  Files         297      299       +2     
  Lines        9060     9075      +15     
  Branches     1848     1851       +3     
==========================================
+ Hits         8422     8435      +13     
- Misses        638      640       +2     

Impacted Files	Coverage Δ
...erimental/packages/shim-opencensus/src/register.ts	0.00% <0.00%> (ø)
experimental/packages/shim-opencensus/src/shim.ts	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

[Flarna]

If moving to @opentelemetry/instrumentation can't be done and RITM is used here it's most likely ok.

@opentelemetry/instrumentation has two main advantages:

• avoid overhead because of multiple RITM hooks (see [@opentelemetry/instrumentation] require performance grows linearly with each instrumentation plugin #3029)
• Hide patching details (e.g. to support CJS and ESM)

One more RITM hook should be not that problematic (compared to >20 one got via autoinstrumentations in the past).

Missing ESM support is maybe also no issue because this shim is to get backward compatibility with a discontinued project where ESM is likely not a big topic anyway.

But we should document that ESM is not working for this shim.

[dyladan]

Implementation looks ok to me. Just some minor comments

[dyladan]

But we should document that ESM is not working for this shim.

I think we talked about it at the meeting last week but documenting here for clarity: opencensus doesn't support ESM so there should be no expectation it works with the shim