feat: add env vars for keepAliveTimeout and headersTimeout (#15125)

feat: add env vars for keepAliveTimeout and headersTimeout (#15125)

* Check for and apply timeouts for keepAlive and headers

* Update docs with new timeout env vars

* Add changeset for new timeouts

* Run the formatter

* Tweak the docs wording a bit

* Check for empty vars before parsing and validating

* Update documentation/docs/25-build-and-deploy/40-adapter-node.md

Co-authored-by: Tee Ming <chewteeming01@gmail.com>
* Add a timeout_env helper with corresponding tests

* fix: convert adapter-node tests to TypeScript for project service compatibility

The tsconfig include pattern with brace expansion {js,ts} was not being
recognized by TypeScript's project service used by ESLint. Split into
separate patterns and converted test files to TypeScript.

* format

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Co-authored-by: Tee Ming <chewteeming01@gmail.com>
Co-authored-by: Elliott Johnson <hello@ell.iott.dev>