cmdline-opts: category cleanup

Option cleanups:

--get is not upload
--form* are post
- added several options into ldap, smtp, imap and pop3
- shortened the category

cmdline-opts: category cleanup

Option cleanups:

--get is not upload
--form* are post
- added several options into ldap, smtp, imap and pop3
- shortened the category descriptions in the list

category curl fixes:

--create-dirs removed from 'curl'
--ftp-create-dirs removed from 'curl'
--netrc moved to 'auth' from 'curl'
--netrc-file moved to 'auth' from 'curl'
--netrc-optional moved to 'auth' from 'curl'
--no-buffer moved to 'output' from 'curl'
--no-clobber removed from 'curl'
--output removed from 'curl'
--output-dir removed from 'curl'
--remove-on-error removed from 'curl'

Add a "global" category:

- Made all "global" options set this category

Add a "deprecated" category:

- Moved the deprecated options to it (maybe they should not be in any
category long term)

Add a 'timeout' category

- Put a number of appropriate options in it

Add an 'ldap' category

- Put the LDAP related option in there

Remove categories "ECH" and "ipfs"

- They should not be categories. Had only one single option each.

Remove category "misc"

- It should not be a category as it is impossible to know when to browse
it.

--use-ascii moved to ftp and output
--xattr moved to output
--service-name moved to auth

Managen fixes:

- errors if an option is given a category name that is not already setup
for in code

- verifies that options set `scope: global` also is put in category
`global´

Closes #14101

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get.d: clarify the explanation

Closes #13706

docs/cmdline: change to .md for cmdline docs

- switch all invidual files documenting command line options into .md,
as the documentation is now markdown-looking.

- made the

docs/cmdline: change to .md for cmdline docs

- switch all invidual files documenting command line options into .md,
as the documentation is now markdown-looking.

- made the parser treat 4-space indents as quotes

- switch to building the curl.1 manpage using the "mainpage.idx" file,
which lists the files to include to generate it, instead of using the
previous page-footer/headers. Also, those files are now also .md
ones, using the same format. I gave them underscore prefixes to make
them sort separately:
_NAME.md, _SYNOPSIS.md, _DESCRIPTION.md, _URL.md, _GLOBBING.md,
_VARIABLES.md, _OUTPUT.md, _PROTOCOLS.md, _PROGRESS.md, _VERSION.md,
_OPTIONS.md, _FILES.md, _ENVIRONMENT.md, _PROXYPREFIX.md,
_EXITCODES.md, _BUGS.md, _AUTHORS.md, _WWW.md, _SEEALSO.md

- updated test cases accordingly

Closes #12751

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