Implements Individual Tool Visibility in Toolbar

[zoeangell]

Added the ability to set a tool's visibility in the toolbar. This was done by adding the visible property to the Python Tool Class and Tool module in bokehjs. We modeled the functionality and implementation of this feature after the toggleable property for InspectTools (e.g. CrosshairTool and HoverTool).

Setting visible=False for a tool will make it not show up in the toolbar, but it will still have its functionality.

To test our feature we wrote Javascript unit tests and integration tests.

Graph with box_edit = BoxEditTool(visible = True)

Graph with box_edit = BoxEditTool(visible = False)

Resolves #8153

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a9b4d0f) 92.58% compared to head (a786b5b) 92.58%.

Additional details and impacted files

@@             Coverage Diff             @@
##           branch-3.4   #13593   +/-   ##
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  Coverage       92.58%   92.58%           
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  Files             325      325           
  Lines           20728    20729    +1     
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+ Hits            19191    19192    +1     
  Misses           1537     1537           

[mattpap]

I need to think about this approach in the context of other ongoing work (e.g. PR #13571), i.e. whether it makes sense for tools to be visible or whether it's their UI representation that should carry this setting.

[mattpap]

I did a little clean up of this PR, deprecated toggleable in favor of the new visible property and fixed aliased properties in bokehjs (previously they didn't allow correct initialization).

[mattpap]

@zoeangell, thanks.