Make code compile with clang-13

Clang-13 rightfully warns that the hasWebuiRoute variable isn't declared
as static.  This commit resolves that, and adds the static keyword so it
can be used in multiple compile units.  It also adds the static keyword
to the privilege registry, and the inline keyword to many methods that
now need it.

clang-format is also updated to version 12 in parse_registies.py, as
that's what CI uses, and what most people have installed.

Tested:
Followed clang-tidy instructions in README.md
"bitbake bmcweb" step now succeeds.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Id43b13606754cb37a404799fce155599ac3a3240