Mesh selection actions

[JanCaha]

Description

Adds two new actions for selecting vertices on Mesh:

• select isolated vertices which are not part of any face
• select all vertices from mesh layer

[github-actions]

🪟 Windows builds ready!

Windows builds of this PR are available for testing here. Debug symbols for this build are available here.

(Built from commit 2965486)

[uclaros]

meshVertexCount() says:

\note during mesh editing, some vertices can be void and are not included in this returned value

does that affect us?
Would it be better to maybe use mCurrentLayer->selectVerticesByExpression( true ) to get the indexes instead?

[JanCaha]

Seems like a good point.

We could avoid evaluating the expression by using mCurrentLayer->nativeMesh()->vertexCount(). That would skip need to use QgsExpression and its evaluation. It is what the mCurrentLayer->selectVerticesByExpression() does internally anyways.

[github-actions]

🪟 Windows builds

Download Windows builds of this PR for testing.
Debug symbols for this build are available here.
(Built from commit 7d94fad)

[qgis-bot]

@JanCaha
This pull request has been tagged as requiring documentation.

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[qgis-bot]

@JanCaha

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[qgis-bot]

@JanCaha
A documentation ticket has been opened at qgis/QGIS-Documentation#9481
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