chore: add scripts/gen-semconv-ts.js to help generate semconv.ts files for unstable semconv consts

[trentm]

Refs: https://github.com/open-telemetry/opentelemetry-js/tree/main/semantic-conventions#unstable-semconv

---

Now that we've established how we want packages to use unstable semconv definitions, we are starting to get PRs adding a local copy of these: #2664, #2668

It is helpful to script this to: make it faster, encourage a common pattern for these local copies, avoid cut 'n paste errors.

An example run of this (for #2668) looks like this:

% ./scripts/gen-semconv-ts.js detectors/node/opentelemetry-resource-detector-aws
Found import of 31 unstable semconv definitions.
Generated "detectors/node/opentelemetry-resource-detector-aws/src/semconv.ts".
Running 'npx eslint --fix src/semconv.ts' to fix formatting.

It will also warn/error on attempts to put stable semconv exports in there. That looks like this:

% ../../../scripts/gen-semconv-ts.js
gen-semconv-ts warning: ./src/detectors/AwsBeanstalkDetectorSync.ts: 'ATTR_SERVICE_NAME' export is available on the stable "@opentelemetry/semantic-conventions" entry-point. This definition will not be included in the generated semconv.ts. Instead use:
    import { ATTR_SERVICE_NAME } from '@opentelemetry/semantic-conventions';
gen-semconv-ts warning: ./src/detectors/AwsBeanstalkDetectorSync.ts: 'ATTR_SERVICE_VERSION' export is available on the stable "@opentelemetry/semantic-conventions" entry-point. This definition will not be included in the generated semconv.ts. Instead use:
    import { ATTR_SERVICE_VERSION } from '@opentelemetry/semantic-conventions';
Found import of 31 unstable semconv definitions.
Generated "src/semconv.ts".

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.80%. Comparing base (4fb610d) to head (4dede11).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2669   +/-   ##
=======================================
  Coverage   90.80%   90.80%           
=======================================
  Files         170      170           
  Lines        8070     8070           
  Branches     1646     1646           
=======================================
  Hits         7328     7328           
  Misses        742      742