[bitmap] Make bitmap a static library and use -fvisibility=hidden

ZX-1895 #comment

Test: cq
Change-Id: Ia4a3ad32e78ac3cbe12bc40c01d55a5e1835d126

[fvm][zxcrypt] Refactor libraries to avoid fdio dependency

ZX-2266 #done

Test: Refactor; relying on exitant library/driver tests.

Change-Id: Ia54acac0fb8056c91b26c097a8efae22dd0c5b3a

[zxcrypt] Don't cache parent block information

This CL removes the copy of the block_info_t from the zxcrypt
device. Caching such information caused it to be invalid after FVM
resizes. This also caused the 'synthetic' block size to be removed,
which hasn't been needed since the Jan. refactor, and which broke
atomicity with lower layers.

ZX-1948 #comment Fixed

Change-Id: I8d2e9ab8eb965f7ead1796eb38d9dc0e6ee939f8

[zxcrypt] enable some integer sanitization

Enable the integer-divide-by-zero (relevant for ARM only) and
signed-integer-overflow checkers. This will add in-code detection for
some classes of undefined integer behavior.

Limit this to zxcrypt for now, as this is just an experiment.

SEC-53: Build a system that is robust against vulnerabilities

Change-Id: I89a5aca790c7325aa5de4d153a1f53036a14c814

[zxcrypt] more moving to compiler intrinsics

See ZX-1747

Change-Id: Idae93cf343fb42560fe83b6faa4e99f4ae35edb8

[zxcrypt] Add encrypted block device filter driver

This CL adds the actual driver and associated tests. The driver consists
of the Device itself, extra fields used to associate I/O requests with
pooled resources used to perform cryptographic transformations, and
threaded workers used to perform that work asynchonously.

Change-Id: Ib1ac05c6abda076359264b861946d23aba98d983