annotate: fix a revision number discrepancy between the margin and statusbar

I'm not sure what's going on here, and it likely is related to hidden revisions
because I hit it in my local thg development repo, but not in a clone of the
upstream repo on another machine. When annotating `tortoisehg/hgqt/thgrepo.py`
from the manifest widget at this revision, the margin at line 39 (which adds
the pycompat import) says the change was at revision 18970 (6a0080d4e5a5), but
the statusbar says it originated in 18963.

That line was added in (the extinct) 18963, but `hg annotate` agrees with the
margin, as does `hg annotate --hidden`. Since the filecontexts are cached in
`_onAnnotateFinished()` with `repo[rev][path]`, where `rev` is the value
returned by the annotate command, I'm not sure why any adjustment would have
been necessary. But it looks like it's been there in some form since ~2010.
This is the only place the hglib function is called, so it won't break anything
else.

version: cache the calculated version information

No sense in recomputing this 5 times for each of the extensions and/or in the
AboutBox, after whatever it is doing on startup.

extensions: report the application version as the bundled thg extension version

Otherwise if commandserver crashes, there's nothing in the stacktrace that
indicates what version of thg was running it- only the core hg version is
relayed. These versions will also show up in `hg version -v` in the console
window, for verification.

version: suppress the message about obsolete feature not being enabled

This printed out one or more times on startup when running from source, or
checking the about box. That was puzzling, since I have the evolve extension
enabled globally (and I didn't realize what was disabling extensions). But I
want to report the thg version in the various thg extensions, because there's
no other way to tell from a bug report what version of thg is running if the
crash is from command server. Without this, the warning message is emitted for
each extension.

hgignore: fix a py3 crash in the untracked files context menu (fixes #5886)

The `self.lclunknowns` field is `List[bytes]`, so that's how the `filters` field
is populated in `menuRequest()`, which in turn is assigned to the `_patterns`
field of QAction, and referenced in `insertFilters()`.

typing: avoid a pytype warning accessing the commit options dictionary

This started getting flagged in pytype 2023.04.11. TypedDict from PEP589 might
be better, but was only accepted in py3.8. There is an alternate syntax that
supports older pythons[1], but I'll leave that for another time.

[1] https://peps.python.org/pep-0589/#alternative-syntax

typing: add an `is not None` assertion to qtlib.py to help pytype

This also started getting flagged by 2023.04.11:

File "/mnt/c/Users/Matt/projects/thg_py3/tortoisehg/hgqt/qtlib.py", line 735, in geticon:
bad option 'None' in return type [bad-return-type]
Expected: PyQt5.QtGui.QIcon
Actually returned: Optional[PyQt5.QtGui.QIcon]
File "/mnt/c/Users/Matt/projects/thg_py3/tortoisehg/hgqt/qtlib.py", line 740, in geticon:
New container type for _iconcache does not match type annotation [container-type-mismatch]
Container: Dict[_K, _V]
Allowed contained types (from annotation Dict[str, PyQt5.QtGui.QIcon]):
_V: PyQt5.QtGui.QIcon
New contained types:
_V: None

Called from (traceback):
line 1222, in set_icon
File "/mnt/c/Users/Matt/projects/thg_py3/tortoisehg/hgqt/qtlib.py", line 741, in geticon:
bad option 'None' in return type [bad-return-type]
Expected: PyQt5.QtGui.QIcon
Actually returned: Optional[PyQt5.QtGui.QIcon]

typing: convert hints on a nested function in visdiff.py to py3 style

Pytype 2023.04.11 started complaining about this for some reason:

File "/mnt/c/Users/Matt/projects/thg_py3/tortoisehg/hgqt/visdiff.py", line 415:
Function type comments cannot be used with annotations [redundant-function-type-comment]