Fix part of #14702: Add the stale tab detection functionality for topic editor page

[soumyo123-prog]

Overview

1. This PR fixes or fixes part of Making changes to a stale topic editor page causes errors #14702
2. This is PR 3 from This design doc
3. This PR does the following:

• Adds the modals for showing stale tab or unsaved changes warning.
• Adds other relevant functions to topic editor page component.
• Adds e2e tests for the functionality.

Essential Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
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• The PR is made from a branch that's not called "develop".

Proof that changes are correct

Screencast.from.10-04-22.04.14.20.PM.IST.mp4

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[oppiabot]

Hi @kevintab95, @nithusha21 -- could one of you please add the appropriate changelog label to this pull request? Thanks!

[soumyo123-prog]

@kevintab95 I have made the changes.

[oppiabot]

Hi @soumyo123-prog. Due to recent changes in the "develop" branch, this PR now has a merge conflict. Please follow this link if you need help resolving the conflict, so that the PR can be merged. Thanks!

[kevintab95]

LGTM, thanks @soumyo123-prog!

[oppiabot]

Hi @soumyo123-prog, the build of this PR is stale and this could result in tests failing in develop. Please update this pull request with the latest changes from develop. Thanks!

[aks681]

Lgtm as codeowner

[oppiabot]

Hi @soumyo123-prog, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 4 days, it will be automatically closed so that others can take up the issue.
If you are still working on this PR, please make a follow-up commit within 4 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[soumyo123-prog]

Dismissing @nithusha21 's review now as their comment (about adding new files in check_frontend_test_coverage.py) is now fixed.

Dismissing @nithusha21 's review now as their comment (about adding new files in check_frontend_test_coverage.py) is now fixed.