refactor(services): eliminate PubSub waste from file watchers - W-22143377

[peternhale]

What does this PR do?

Replace centralized PubSub file/settings watchers with scoped, per-consumer watchers:

• sourceTrackingStatusBar: scope watchers to package directories via RelativePattern, filter with .forceignore, add callback-level debounce and in-flight cancellation ({ switch: true }). Eliminates ~45K wasted events and ~15-17 redundant getStatus calls during npm install.
• aliasFileWatcher / configFileWatcher: use direct createFileSystemWatcher scoped to .sfdx/.sf paths instead of subscribing to global PubSub.
• lwcFileWatcher / testResultsFileWatcher: replace PubSub subscription with scoped glob watchers (**/lwc/**/*.{js,ts,html,js-meta.xml}, **/.sfdx/tools/testresults/apex/*.json).
• configWatcher / logAutoCollect: subscribe directly to onDidChangeConfiguration with pre-filtered callbacks instead of global SettingsChangePubSub.
• Delete fileChangePubSub, fileWatcherService, settingsChangePubSub, settingsWatcherService and their exports.

What issues does this PR fix or reference?

@W-22143377@

Functionality Before

Global **/* file watcher fires ~45K events during npm install, each pushed through Effect PubSub, producing ~15-17 redundant getStatus calls.

Functionality After

Zero getStatus calls from file watcher during npm install. Only the 60s poll stream triggers status checks, which is the intended behavior.