build(test-utils): marking test-utils as non private so it can be published

[blumamir]

Follows #596

Which problem is this PR solving?

• Publish test-utils as a package on NPM #595
• chore: upstream mocha instrumentation testing plugin from ext-js #621
  To my knowledge, there was no objection for it to be published to npm.
  We can discuss here or on the original issue if this is not ok for any reason

Short description of the changes

• mark test-utils as non private (so it can be published to npm)
• add missing LICENCE file
• add "files" section to package.json to state which files should be included in a release
• rename test-utils to contrib-test-utils

[codecov]

Codecov Report

Merging #639 (97a1efc) into main (d711127) will decrease coverage by 1.46%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #639      +/-   ##
==========================================
- Coverage   96.68%   95.22%   -1.47%     
==========================================
  Files          13       67      +54     
  Lines         634     4582    +3948     
  Branches      124      426     +302     
==========================================
+ Hits          613     4363    +3750     
- Misses         21      219     +198     

Impacted Files	Coverage Δ
...oud/test/detectors/AlibabaCloudEcsDetector.test.ts	94.44% <ø> (ø)
...or-aws/test/detectors/AwsBeanstalkDetector.test.ts	100.00% <ø> (ø)
...detector-aws/test/detectors/AwsEc2Detector.test.ts	95.16% <ø> (ø)
...detector-aws/test/detectors/AwsEcsDetector.test.ts	100.00% <ø> (ø)
...detector-aws/test/detectors/AwsEksDetector.test.ts	100.00% <ø> (ø)
...ector-aws/test/detectors/AwsLambdaDetector.test.ts	100.00% <ø> (ø)
...ce-detector-gcp/test/detectors/GcpDetector.test.ts	100.00% <ø> (ø)
...ntelemetry-instrumentation-pg/test/pg-pool.test.ts	91.42% <100.00%> (ø)
...e/opentelemetry-instrumentation-pg/test/pg.test.ts	95.01% <100.00%> (ø)
.../opentelemetry-instrumentation-mysql2/src/utils.ts	100.00% <0.00%> (ø)
... and 53 more

[willarmiros]

LGTM. @dyladan hopefully this can go out in contrib release 0.25.0 so we can unblock the ext-js migrations ASAP!

[blumamir]

LGTM. @dyladan hopefully this can go out in contrib release 0.25.0 so we can unblock the ext-js migrations ASAP!

@dyladan Fixed the conflicts and now tests are green