Move instrumentation-web-exception from contrib to this repo

[martinkuba]

Sub-issue of #209.

Move @opentelemetry/instrumentation-web-exception from opentelemetry-js-contrib into the @opentelemetry/browser-instrumentation package as a subpath export.

Checklist

• Move code to this repo
  • Add instrumentation code to packages/instrumentation/src/errors/
  • Add subpath export (./experimental/errors) to package.json
  • Adapt code to repo conventions (logs-based event API, vitest, tsdown build, shared test utils)
  • Add/port tests
• Deprecate the js-contrib package
  • Update the browser-instrumentation README with docs for the new instrumentation
  • Update the contrib package README with deprecation notice and migration instructions, publish a final version
  • Run npm deprecate on @opentelemetry/instrumentation-web-exception pointing to the new location
  • Delete instrumentation-web-exception package source from opentelemetry-js-contrib