CI: add whitespace checker

Fix issues detected.

Also:

- One of the `.vc` files used LF EOLs, while the other didn't.
  Make that one also use LF EOLs, as this is apparently supported by
  `nmake`.

- Drop `.dsw` and `.btn` types from `.gitattributes`.
  The repository doesn't use them.

- Sync section order with the rest of files in
  `tests/certs/EdelCurlRoot-ca.prm`.

- Indent/align `.prm` and `.pem` files.

- Delete dummy `[something]` section from `.prm` and `.pem` files.

Mental note:
MSVC `.sln` files seem to accept spaces for indentation and also support
LF line-endings. I cannot test this and I don't know what's more
convenient when updating them, so left them as-is, with specific
exclusions.

Closes #14031

.gitattributes

@@ -2,7 +2,6 @@
 #
 # SPDX-License-Identifier: curl
 
-*.dsw -crlf
 buildconf eol=lf
 configure.ac eol=lf
 *.m4 eol=lf
@@ -11,8 +10,7 @@ configure.ac eol=lf
 *.sh eol=lf
 *.[ch] whitespace=tab-in-indent
 
-# Batch files (bat,btm,cmd) must be run with CRLF line endings.
+# Batch files (bat,cmd) must be run with CRLF line endings.
 # Refer to https://github.com/curl/curl/pull/6442
 *.bat text eol=crlf
-*.btm text eol=crlf
 *.cmd text eol=crlf