Remove timers-ext dependency

[GrahamCampbell]

No description provided.

[Copilot]

Pull request overview

This PR removes the external timers-ext dependency by introducing an internal lib/utils/sleep helper and updating runtime + test code to use it.

Changes:

• Drop timers-ext from package.json.
• Add lib/utils/sleep.js and update production code to require it instead of timers-ext/promise/sleep.
• Update tests to import/stub the new sleep helper and add dedicated unit coverage for it.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/utils/misc.js	Switch test helper to use internal lib/utils/sleep.
test/unit/lib/utils/sleep.test.js	Add unit tests for new lib/utils/sleep behavior.
test/unit/lib/plugins/aws/logs.test.js	Update proxyquire stub to match new sleep import path.
test/unit/lib/plugins/aws/deploy-function.test.js	Update modulesCacheStub to stub the resolved lib/utils/sleep.js module path.
test/unit/lib/configuration/variables/resolve.test.js	Replace timers-ext sleep import with internal sleep.
test/unit/lib/aws/request.test.js	Update proxyquire stubs to ../utils/sleep.
test/lib/setup-fixtures-engine.js	Replace timers-ext sleep import with internal sleep.
test/lib/aws-request.js	Replace timers-ext sleep import with internal sleep (used for retry backoff).
test/integration/aws/websocket.test.js	Replace timers-ext sleep import with internal sleep.
scripts/serverless.js	Replace timers-ext sleep import with internal sleep.
package.json	Remove timers-ext dependency.
lib/utils/sleep.js	New internal sleep utility with timeout normalization + max-timeout guard.
lib/plugins/aws/logs.js	Replace timers-ext sleep import with internal sleep.
lib/plugins/aws/lib/wait-for-change-set-creation.js	Replace timers-ext sleep import with internal sleep.
lib/plugins/aws/lib/monitor-stack.js	Replace timers-ext sleep import with internal sleep.
lib/plugins/aws/deploy-function.js	Replace timers-ext sleep import with internal sleep.
lib/aws/request.js	Replace timers-ext sleep import with internal sleep (retry backoff).

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