Extended #region support (outline, refactor region name)

[trulysinclair]

Currently regions, denoted by //#region &| //region, while supported are still lacking in "full support". This definition varies from dev to dev, but I think in more general terms we should be looking at at least "Rename Symbol" or F2 support and outline/breadcrumb support. This would allow larger regioned code to be viewed within outlines. Allowing collapsibility just like the others (method, class, etc...) would also permit less scrolling.

"Rename Symbol"

This one should really be determined by the existence of #region <name>. If the region header and footer both have the same name, then rename both from either the footer or header.

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This should really just expand upon #51364

[jrieken]

This is a duplicate. Unfortunately, I don't recall the exact issue number nor its title 😳 Anyways, searching for issues with the same labels will likely help you 👉
https://github.com/microsoft/vscode/issues?utf8=✓&q=is%3Aopen+label%3Afeature-request+label%3Aoutline