release-23.2: ui: enable Forward button to set timewindow for latest NOW value

[blathers-crl]

Backport 1/1 commits from #112954 on behalf of @koorosh.

/cc @cockroachdb/release

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Before, "Forward" button on Time selector component allowed to select next time window if there's enough space for full increment (ie with 10 min time window, it wasn't possible to move forward if current end time is less that Now() - 10min). It caused misalignment where Forward button became disabled even if there's some more data to display.

This change handles this case and updates current time window to current time (executes the same logic as Now button).

Resolves: #112847

Release note (ui change): Forward button on time selector allows to select latest available timewindow (the same as with "Now" button)

Release justification: low risk, high benefit changes to existing functionality

Screen.Recording.2023-10-24.at.14.00.36.mov

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Release justification: low risk, high benefit changes to existing functionality

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

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[cockroach-teamcity]

This change is