Problem:
"set filetype=man" assumes the user wants :Man features, this does extra
stuff like renaming the buffer as "man://".

Solution:
- old entrypoint was ":set filetype=man", but this is too presumptuous #15487
- make the entrypoints more explicit:
  1. when the ":Man" command is run
  2. when a "man://" buffer is opened
- remove the tricky b:man_sect checks in ftplugin/man.vim and syntax/man.vim
- MANPAGER is supported via ":Man!", as documented.

fixes #15487

Update runtime files
https://github.com/vim/vim/commit/3ec3217f0491e9ba8aa8ea02f7e454cd19a287ef

Omit fuzzy-match in pattern.txt.

Update runtime files
https://github.com/vim/vim/commit/4c295027a426986566cd7a76c47a6d3a529727e7

Update runtime files
https://github.com/vim/vim/commit/11e3c5ba820325b69cb56f70e13c21d7b8808d33

Update runtime files.
https://github.com/vim/vim/commit/56994d215815139207f3c5ce02a1720e44e93c09

Update runtime files
https://github.com/vim/vim/commit/130cbfc31235c6cb52ffe718ea0a5bb50fbbc9fd

Update runtime files.
https://github.com/vim/vim/commit/dad4473f02e1fec86d43a2fc094536a4b27d3b25

Omit :echoconsole. Patch v8.2.2638 is not ported.

Update runtime files.
https://github.com/vim/vim/commit/c8cdf0f80b3cfd88a4490d80572062c1fd1a96ca

Update runtime files.
https://github.com/vim/vim/commit/9faec4e3d439968e21ad74e917aebb289df8f849

Omit vim9.

Update runtime files
https://github.com/vim/vim/commit/942db23c9cb7532d68048530d749eb84ca94d0cd

Omit po files.