kconfig: Make header comments consistent globally

[ulfalizer]

Similar deal to #20266,
cleaning up all header comments to use a consistent format. Also includes some
stuff I missed in the first PR.

Main commit:

kconfig: Clean up header comments and make them consistent

Use this short header style in all Kconfig files:

    # <description>

    # <copyright>
    # <license>

    ...

Also change all <description>s from

    # Kconfig[.extension] - Foo-related options

to just

    # Foo-related options

It's clear enough that it's about Kconfig.

The <description> cleanup was done with this command, along with some
manual cleanup (big letter at the start, etc.)

    git ls-files '*Kconfig*' | \
        xargs sed -i -E '1 s/#\s*Kconfig[\w.-]*\s*-\s*/# /'

Other stuff:

kconfig: Clean up 'config  FOO' (two spaces) definitions

Must've been copy-pasted around.

kconfig: Change some '#Comment' comments to '# Comment'

For consistency. Newly-introduced stuff.

[finikorg]

@ulfalizer Could you document templates in the Zephyr documentation?

Added documentation for the header format. See the new doc: kconfig: Document recommended header format commit.

Thanks! That is what I meant.