Update reference to micro-states

[syl20bnr]

From @balajisivaraman on #4883

The term micro-state was still being referred to all over the codebase. So I've created this PR in-order to change all of them to transient-state in order to ensure consistency, and also for feedback in case I screw something up. 😃

• Change all .org files in doc folder to refer to transient states
• Change all layer-specific README files to refer to transient states
• There are some variables across the codebase (For eg: some faces vars) that refer to micro-states. I can change these as well if it's OK with you folks.
• There are places such as ido and workspaces that refer to micro-states, even though they have been changed to transient states. These might need to be verified to ensure they are not bugs.
• Magit-blame mode is still a micro-state (only one left). So I've not changed anything related to it as of now.
• Right now the screenshot files used have simply been renamed. But they should probably be taken anew as well. I'll do that.

[deb0ch]

Autumnal cleanup: Is this issue still relevant ?

[github-actions]

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