Update lacros to use static mime cache

When lacros looks up mime type from file extension, it is currently
reading from /usr/share/mime/mime.cache. We have recently added an
equivalent static map which is used by ash which is also available for
lacros to use. This approach has the performance and security advantage
that there is no need to read a system file.

Bug: 1015353
Change-Id: I625342d2f68386df6d8cc78a389b61b7354aa3f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3890051


Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1046023}