fix: use faas.instance instead of faas.id in resource detectors

[dashpole]

Part of GoogleCloudPlatform/opentelemetry-operations-go#679

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[codecov]

Codecov Report

Merging #600 (39bd501) into main (f72e2e1) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 39bd501 differs from pull request most recent head b829e8d. Consider uploading reports for the commit b829e8d to get more accurate results

@@           Coverage Diff           @@
##             main     #600   +/-   ##
=======================================
  Coverage   97.68%   97.68%           
=======================================
  Files          18       18           
  Lines         691      691           
  Branches      127      127           
=======================================
  Hits          675      675           
  Misses         16       16           

Files Changed	Coverage Δ
packages/opentelemetry-resource-util/src/index.ts	100.00% <ø> (ø)
...entelemetry-resource-util/src/detector/detector.ts	100.00% <100.00%> (ø)
...s/opentelemetry-resource-util/src/detector/faas.ts	96.15% <100.00%> (ø)

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