mail/py-alot: Update to 0.12

alot 0.9 imports the mailcap module, which was removed in Python 3.13.
0.12 supports Python 3.13 and 3.14 and depends on standard-mailcap
there.

• Switch to USE_PYTHON=pep517 with setuptools-scm
• Use mail/py-notmuch2 instead of the legacy mail/py-notmuch
• Add mail/py-standard-mailcap for Python >= 3.13
• Depend on urwid>=1.3.0 directly and on urwidtrees>=1.0.3, as 0.12 requires
• Add concurrent to USE_PYTHON (bin/alot is installed)

PR: 299759
Approved by: Dhananjay Balan <mail@dbalan.in> (maintainer)