Add page locks to Layout palette

[davidstephengrant]

Your idea

Lock/unlock selected page(s) should be added to the Layout palette, e.g. to the right of Lock/unlock selected system(s).

Problem to be solved

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As part of this, let's also move Keep bars on the same system back out from More to the main Layout palette. It can go to the right of Section break.

Prior art

No response

Additional context

Depends on: #33737

Checklist

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