Support -TRIAL in versions for [NextRelease]

Adopted the same syntax as from various Git plugins (e.g. [Git::Commit],
except %t was already being used for tab, so switched to %T. ([Git] should
probably adopt %T, as %t for tab is pretty standard.)
Also added %V to allow justification on the combined version-TRIAL string,
although I suspect that String::Formatter can handle this in a better way.
Add %E & %U format codes to NextRelease

  Add user_stash attribute
  Clean up documentation
Fix nextrelease.t to use Test::Fatal

  Otherwise, the test is quietly skipped instead of failing
Test %E & %U format codes in NextRelease
Remove __END__ markers

  Pod::Weaver likes to insert those itself.  Otherwise, the POD will be
  placed before the __END__ marker.
Mention OurPkgVersion in PkgVersion
v4.300018

          format codes %E, %T, %U, & %V added to NextRelease (thanks,
          Karen Etheridge & Christopher J. Madsen!)
don't look in the user's global config when testing
make sure to use the share dirs from the repo for testing
better diagnostics when this test fails
v4.300019

          avoid looking outside the dist during testing (thanks, Jesse Luehrs!)
the working directory needs to be set for test too
v4.300020

          properly set the working directory when testing (thanks, Jesse
          Luehrs!)
typo fix; thanks, dolmen!
do not compile-test the tutorial
More ManifestSkip tests

Compare with/without [ManifestSkip]
Add test showing RT#76036 (ManifestSkip and generated files)

Add 2 tests that show bug RT#76036.
By the way, the test also tests DZP::InlineFiles.
RT#76306: Plugins can now generate MANIFEST.SKIP files

When the content of MANIFEST.SKIP has been generated by plugins
(such as an InlineFiles plugin), the content is saved as a
temporary file before being fed to EU::Manifest::maniskip.
Changes for RT#76036
remove TODO in tests for RT#76036