Fix contrast of debugger icon when selected

[krassowski]

The debugger icon does not have proper contrast when items with this icon are selected. This PR fixes it by adding jp-icon-selectable class.

Code changes

N/A

User-facing changes

Before:

After:

Backwards-incompatible changes

N/A

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Thanks!

[bollwyvl]

Nice fix... so over on some other stuff, I found a lot of debugger styles are pretty inflexible... still mired in #9779, but might take a crack at it.

However: (and germane to #9779) debugger has some great stuff for making a DataGrid look good in the face of theming (didn't know i was using even using it!), but it's all hidden under private methods... it would be awesome if there was a ui-components ThemedDataGrid or something that encapsulated that behavior.

Also @krassowski: we'd need to land a bunch of changes to debugger if we want to do any gutter work on lsp, as it kinda stomps over everything.

[jtpio]

debugger has some great stuff for making a DataGrid look good in the face of theming (didn't know i was using even using it!), but it's all hidden under private methods... it would be awesome if there was a ui-components ThemedDataGrid or something that encapsulated that behavior.

Yeah I think the idea was to extract it into its own plugin so it could also be used for the csv viewer (or any other plugin).