feat(amazonq): Implement backslash abstraction

[laura-codess]

Change

Implemented backslash.test.ts which is the test suite where all the menu overlay tests will live. In order to implement this test suite, I also added dismissOverlay to cleanupHelper.ts. It is not fully matured yet because I noticed that the menu overlay is being actively changed as of right now.

NOTE: This PR depends on #7685

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[github-actions]

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[Hweinstock]

I'm assuming this is dependent on #7685? Could be worth explicitly calling this out in the PR.