fix: removed support for experimental loader flag

[aryamohanan]

BREAKING CHANGE

• Dropped support for --experimental-loader
• Dropped support for esm-loader.mjs file

Notes:

--experimental-loader is already not working for Node versions >= v18.19.0 (documented already)
esm-loader.mjs works with --experimental-loader only.
We are dropping support for < v18.19.

Reference

Node.js Version	Loader Command	Tracing Behavior Before(v5)	Tracing Behavior After(v5)	Notes
18.18	--experimental-loader ./node_modules/@instana/collector/esm-loader.mjs	✅ Worked	❌ No longer works	18.18 support dropped in v5.
18.18	--import ./node_modules/@instana/collector/esm-register.mjs	❌ Already didn’t work	❌ Still doesn’t work	register api not available in earlier versions
18.19+	--experimental-loader ./node_modules/@instana/collector/esm-loader.mjs	❌ Already didn’t work	❌ Still doesn’t work	ESM off-thread; early tracer exit with error log in v5.
18.19+	--import ./node_modules/@instana/collector/esm-register.mjs	✅ Works	✅ Works	Recommended approach for Node ≥18.19; ensures ESM tracing.
18.19+	autotrace set to module_v1	❌ Already didn’t work	❌ Still doesn’t work	ESM off-thread; early tracer exit with error log in v5.

Autotrace webhook: https://github.ibm.com/instana/autotrace-mutating-webhook/pull/670

[kirrg001]

suggestion:

introduced breaking changes

IMO this is too much information without a link to their breaking change.

Thats why IMO:

For Node.js versions later than 18.19, the --experimental-loader flag and ESM support are no longer available.

[kirrg001]

The use case here is:

--import esm-loader.mjs

Right?

Its very nice to catch the wrong usage - especially because we drop the syntax.

I feel like the error message is not on point?

[kirrg001]

We need a todo to cleanup task for internal Github usages of "--experimental-loader".