Cleanup: clearTimeout on useEffect for gas estimation and prevent state update on unmounted ConfirmTransactionBase

[digiwand]

Explanation

• Clears timeout in gas estimation useEffect hook to prevent memory leak
• Fix ConfirmTransactionBase error message: "Can't perform a React state updated on an unmounted component"

Screenshots/Screencaps

Before

warnings still exist after this PR, it should be less frequent.

After

Manual Testing Steps

• Create transactions
• Interact with transactions by rejecting or confirming
• Observe console

Pre-merge author checklist

• I've clearly explained:
  • What problem this PR is solving
  • How this problem was solved
  • How reviewers can test my changes
• Sufficient automated test coverage has been added

Pre-merge reviewer checklist

• Manual testing (e.g. pull and build branch, run in browser, test code being changed)
• PR is linked to the appropriate GitHub issue
• IF this PR fixes a bug in the release milestone, add this PR to the release milestone

If further QA is required (e.g. new feature, complex testing steps, large refactor), add the Extension QA Board label.

In this case, a QA Engineer approval will be be required.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [fcb1c75]

• builds: chrome, firefox
• builds (beta): chrome, firefox
• builds (flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4
  • common: 0, 1, 2, 3, 4, 5
  • content-script: 0
  • contentscript: contentscript
  • disable-console: disable-console
  • inpage: inpage
  • policy-load: policy-load
  • sentry-install: sentry-install
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (1460 ± 66 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	96	164	114	16	8
		domContentLoaded	1234	1893	1448	129	62
		load	1234	1932	1460	137	66
		domInteractive	1234	1893	1448	129	62

Bundle size diffs

• background: 0 bytes
• ui: 69 bytes
• common: 0 bytes