[CIR][NFC] Upstream LValueBaseInfo handling (#134928)
Previous implementations that used the cir::LValue class omitted hanling
of the LValueBaseInfo class, which tracks information about the basis
for the LValue's alignment. As more code was upstreamed from the
incubator, we were accumulating technical debt by adding more places
where this wasn't handled correctly. This change puts the interfaces in
place to track this information.
The information being tracked isn't used yet, so no functional change is
intended. The tracking is being added now because it will become more
difficult to add it as more features are implemented.
