ci: "Failed to watch node_modules/…/package.json using fs.watch() … ENOSPC"

## Problem

The `Linux Unit Tests` CI jobs show these (non-fatal, currently) errors indicating that something is crawling files in `node_modules` and trying to watch `package.json`

```
[File Watcher (parcel)] Inotify limit reached (ENOSPC) (path: /codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules)
file_editAwsFile telemetry
[File Watcher (node.js)] Failed to watch /codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/readline-sync/package.json for changes using fs.watch() (Error: ENOSPC: System limit for number of file watchers reached, watch '/codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/readline-sync/package.json')
[File Watcher (node.js)] Failed to watch /codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/responselike/package.json for changes using fs.watch() (Error: ENOSPC: System limit for number of file watchers reached, watch '/codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/responselike/package.json')
[File Watcher (node.js)] Failed to watch /codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/retry/package.json for changes using fs.watch() (Error: ENOSPC: System limit for number of file watchers reached, watch '/codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/retry/package.json')
[File Watcher (node.js)] Failed to watch /codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/semver/package.json for changes using fs.watch() (Error: ENOSPC: System limit for number of file watchers reached, watch '/codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/node_modules/@types/semver/package.json')
Unable to load and parse grammar for scope source.ssmjson from file:///codebuild/output/src4054755577/src/github.com/aws/aws-toolkit-vscode/packages/core/syntaxes/SSMJSON.tmLanguage { fileOperationResult: 1, options: { preferUnbuffered: true } }
✔ emits when opened by user (488ms)
```

# Expected behavior

Toolkit/Q code should not create lots of file watchers. #2382 (Good news: this may be a CI-only issue; see "Analysis" below.)

This issue is currently not "fatal" (doesn't fail CI or interfere with tests ... yet). But:

1. it may point to a problem that affects actual users (on Linux if not other OSes)
2. it adds noise to the CI logs
3. it may interfere with tests in the future

# Analysis

- The `…/aws-toolkit-vscode/node_modules/…/package.json` paths indicate that this may be happening from the test runner or other tooling, rather than the Toolkit application code. Because that isn't the "test workspace", that's the source tree.
- This suggests that this may be a CI-only problem.
- No effect from [disabling all calls to createFileSystemWatcher()](https://github.com/aws/aws-toolkit-vscode/pull/5491/commits/9a4569124b66f7b657f5244b67e5a5ecde75f96b) in our code.
- No effect from [overriding fs.watch](https://github.com/aws/aws-toolkit-vscode/pull/5491/commits/5747ac86a7cf4064fb6b8058983d11c5c67e6733).
- Our `watchedFiles` modules suffers from the fact that its "exclude" feature doesn't actually prevent watchers from being created. it only skips the events at runtime.
- The docs for `createFilesystemWatcher` indicate that recursive patterns for a workspace are supposedly handled by vscode to avoid duplicate watchers ?
- This may be a linux-only issue? see:
- https://github.com/microsoft/vscode/issues/162567
- "To find out a culprit which is wasting your watchers you can use https://github.com/fatso83/dotfiles/tree/master/utils/scripts#inotify-consumers"

Start with the Linux Unit Tests CI job and the watchedFiles module, then inspect createFileSystemWatcher usage and the linked experiments disabling createFileSystemWatcher and overriding fs.watch. Trace which tooling watches node_modules and verify that the ENOSPC messages disappear without changing test behavior.

Written by the indexing model from the issue text.