fix(windows): sentry.dll version handling

Fixes #5166.

This introduces versioned management of sentry.dll for Keyman for
Windows, Keyman Engine and Keyman Developer. As sentry.dll's ABI is not
backwardly compatible, we have to maintain independent copies of each
DLL for each app.

sentry.dll (or sentry.x64.dll for x64 apps) will be found in the
sentry-0.4.9 folder relative to the running process, except when running
from within the keyman repo tree (based on presence of KEYMAN_ROOT env
var). In those cases, the windows/src/ext/sentry sentry.dll will be
used, allowing us to test new debug time sentry DLLs easily.

A little bit of cleanup and consolidation was also done in the
KeymanPaths.pas unit.