Make tooltips from all editor modes inform about the selection menu shortcut

[YeldhamDev]

As highlighted by #99795 (comment), the tooltips for modes in the Node 3D editor already tell you about the menu selection shortcut, so having the "(Available in all modes.)" in the Selection mode tooltip was pointless. So this PR:

• Removes "(Available in all modes.)" note in the Selection mode tooltip.
• Makes the modes in the CanvasItem editor tell you about the shortcut, to match the 3D editor.
• Removes unnecessary tooltips that are just repeating what the shortcut is saying (small bonus).

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Fun fact: the original notes about the shortcut in the 3D editor erroneously said that it showed locked nodes, which wasn't the case before that PR, and is something that I forgot to document on it (oops). But since people thought that's how it worked anyways, no harm done I guess? 😜

[ryevdokimov]

Looks good.

[KoBeWi]

Removes unnecessary tooltips that are just repeating what the shortcut is saying (small bonus).

So as it turns out, which is probably why we have a check for tooltip matching the shortcut name, if a button has an empty shortcut, it will not show any tooltip at all.

godot.windows.editor.dev.x86_64_GmMNZaNYYm.mp4

With default shortcut removed:

TeY38A51vC.mp4

I'd leave that for another PR, as it requires some re-thinking of the behavior. You can however tweak the tooltips to match shortcut names for buttons that don't already.

There's also this:

But there is no way to solve that right now.

EDIT:
I opened #101468
If it's merged first, this PR can be merged without further changes.