Enable "Search Cell Outputs" in Find/Replace, disable "Replace" button when an output is highlighted

[Tanmay-Deshmukh]

Fixes #15966
Closes #15445

Changed searchprovider.ts in notebook package to allow for searching cell outputs while replace is active. Passed information on currently highlighted string and if it is an output to replace overlay to disable "Replace" button when highlighting an output.

Replace is disabled but not grayed out when highlighting an output due to what I believe to be a styling issue.

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[JasonWeill]

@Tanmay-Deshmukh Thank you for opening this PR! I checked out your code. I think the "styling issue" you noted in your description should be fixed as part of this change. I appreciate that I can still search in cell outputs when the replace options are visible, but the "Replace" button should be visibly disabled (different color, different cursor, tooltips, etc) when I'm currently looking at a cell output result. In addition, I don't see a highlight to indicate which result is actively selected when I'm iterating through results in cell outputs. The "Replace All" button should be disabled if the only results are inside cell outputs, since none of these can be replaced.

[krassowski]

(I shortened the PR title as we also use them to auto-generate changelog)

[krassowski]

@Tanmay-Deshmukh are you interested in finishing up this PR? It is ok to say no, I just need to make a quick update on this one for release planning.

[krassowski]

Based on the review from @JasonWeill which I interpret to mean "changes need to be made" I am switching this PR to draft. Please undraft when the changes are addressed :)