chore(windows): Update Sentry to 0.4.9

Fixes #4607.

The Sentry 0.4.9 update actually simplifies some things. It does only
build with VS2019 by default, which pushed me to update Keyman build to
the same version, but that's a good thing overall, and was fairly
painless anyway.

Previously, we had our own custom build of sentry-native to make sure
that the C++ runtime libraries were statically linked to sentry.dll, but
this is now configurable in the build options, so we were able to
abandon our fork of the project at
https://github.com/keymanapp/sentry-native, which is good news. (I will
leave the fork there just in case but we'll eventually delete it once we
are convinced that this is robust.)

I have updated sentry.pas to match sentry.h; most of the changes are in
comments but there are a handful of new functions and some small changes
to function signatures.

I retested the Sentry exception scenarios and results can be found at
https://docs.google.com/spreadsheets/d/19xfurbn4cGubSCD68EGuKhcR5HrjaUcY/edit#gid=170604584

There may be an issue with Delphi x64 programs missing symbols from my
machine; something to keep an eye on but not a blocker for this merging,
I think.