[enhancement][js] Ensure auto-instrumentation is functional in ESM-only projects

[cephalization]

Packages are now advertised as ESM, but does auto-instrumentation work under ESM-only projects?

While we build and ship ESM versions of our packages, we do not advertise their availability to module resolvers via package.json

We need to fill out the exports field.

See:

• https://docs.npmjs.com/cli/v10/configuring-npm/package-json#exports
• https://nodejs.org/api/packages.html#conditional-exports
  • Conditional exports allow us to point to esm builds when import-ing and cjs builds when require-ing

[cephalization]

Additionally, we should evaluate if esm support actually works correctly.

See https://github.com/open-telemetry/opentelemetry-js/blob/main/doc/esm-support.md

for what the implications are when using these packages in esm-only applications

[cephalization]

Also see #1144