ci: update GHA configuration

[ralphlange]

MacOS:

• remove macos-11 (dropped) and macos-12 (deprecated)
• add macos-13, macos-14, macos-15

[mdavidsaver]

wrt. the failed patch. I saw this before with #97, but didn't scroll up far enough to notice...

.DEBUG:cue:EXEC 'patch -p1 -i /Users/runner/work/ci-scripts/ci-scripts/test.patch' in hook_test
Files: 1
Size:       13
Compressed: 285
Applying patch /Users/runner/work/ci-scripts/ci-scripts/test.patch in hook_test
patching file bla.txt
1 out of 1 hunks failed--saving rejects to bla.txt.rej
patching file 'dd/new.txt'

[ralphlange]

Duh! I thought that the 'patch' utility wasn't installed in the newer MacOS images... silly.

[ralphlange]

Merged with 4e4f33e