Problem:  No tests for the termdebug plugin
Solution: Add some simple tests for the termdebug plugin

closes: vim/vim#12927

https://github.com/vim/vim/commit/58f39d89a8adff51ab04893d1fd28e3767979f9f

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

It is no longer needed now that luarocks isn't used.

- adjust reviewers
- add workflow as cache key
- install attr only when tesitng
- fix s390x workflow by checking out the merge PR instead of master

- add reviewers
- correct cache key

Problem:  No support for writing extended attributes
Solution: Add extended attribute support for linux

It's been a long standing issue, that if you write a file with extended
attributes and backupcopy is set to no, the file will loose the extended
attributes.

So this patch adds support for retrieving the extended attributes and
copying it to the new file. It currently only works on linux, mainly
because I don't know the different APIs for other systems (BSD, MacOSX and
Solaris).  On linux, this should be supported since Kernel 2.4 or
something, so this should be pretty safe to use now.

Enable the extended attribute support with normal builds.

I also added it explicitly to the :version output as well as make it
able to check using `:echo has("xattr")`, to have users easily check
that this is available.

In contrast to the similar support for SELINUX and SMACK support (which
also internally uses extended attributes), I have made this a FEAT_XATTR
define, instead of the similar HAVE_XATTR.

Add a test and change CI to include relevant packages so that CI can
test that extended attributes are correctly written.

closes: vim/vim#306
closes: vim/vim#13203

https://github.com/vim/vim/commit/e085dfda5d8dde064b0332464040959479696d1c

Co-authored-by: Christian Brabandt <cb@256bit.org>

This will fix the failing release job.

Ubuntu 18.04 is incompatible with checkout action version 4, which
requires glibc 2.28+. This will bump the minimum glibc version required
to use the release versions to 2.31. People requring the older releases
can find them at https://github.com/neovim/neovim-releases.

GitHub paginates responses with many results, which needs to be taken
into account as the number of events in an issue can be large.