Move sensitive policy definition to YAML files.

This change refactors how "sensitive policies" are defined. Instead of a
hardcoded list in `policy_loader_common.cc`, a new `sensitive: true`
field is added to the policy's YAML definition. The policy generation
scripts are updated to read this field and generate the list of
sensitive policies, which is then exposed via `GetSensitivePolicies()`.
The list of generated policies is platform-specific. This improves
maintainability by keeping policy attributes within their respective
YAML files.

Fixed: 40915965
Change-Id: If9641881dd004d7b96af7bd902fe04a9ee9dc5ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6915497
Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Yann Dago <ydago@chromium.org>
Commit-Queue: Alex Chyrtsik <alexchy@google.com>
Cr-Commit-Position: refs/heads/main@{#1511596}