[cprng] Update clients to zx_cprng_draw

Test: cprng, chromeos-disk-setup
Change-Id: I8fffa468ceec58a371c8eaa0c6bbdaa204e77df8

[cprng] Remove short reads from zx_cprng_draw

We never actually generate short reads from zx_cprng_draw. This CL
removes the |actual| out parameter. Now zx_cprng_draw either fails or
succeeds in drawing the amount requested, simplifying clients and
removing possible mistakes.

This CL is phase 1 of the transition, which introduces the new version as
zx_cprng_draw_new. Once all the clients are migrated, we'll change
zx_cprng_draw itself, migrate all the clients back, and then remove
zx_cprng_draw_new.

Change-Id: I2219d0517f103fb999014de1e846fa8b8a5ca20c

[crypto] Split Bytes class

This CL breaks out the Secret class from the Bytes class. A number of
paranoid but expensive functions are only needed for security sensitve
secrets, e.g. mandatory_memset in the destructor of keys. This split
allows only the data that needs the paranoia to pay for it.

Change-Id: Ib3fdc23ef7c0f86a6549c639353ac72bb35ebedf

[crypto][zxcrypt] Remove Bytes::Increment

This CL removes the method was being used for incrementing the IV used
by AEAD and Cipher. As written, it was too general purpose and slow in
order to be constant time. In its place, AEAD and Cipher now represent
their IVs as an array of zx_off_ts, and only increment the first one.
this is much quicker (and still safe) as it is only an add and a store.
This limits both of them to 2^64 cryptographic operations, but in
practice this likely won't be a concern.

Change-Id: I9ed707a2aa71aae619906af5918f3d8e5451b3d5

[fdio] Move headers into lib/fdio/...

Change-Id: Ie8d74e716da913bf6e2672c4acf8cd67b4962b7f

[crypto][zxcrypt] Remove Bytes::Split,Append

This CL removes the Split and Append methods from Bytes. They were only
used in a single place, zxcrypt::Volume, and werne't being test due to
an oversight. The same behavior can be achieved with simple Copy()s.

Change-Id: Ie73151122a27ec481a0cf38daf7bf3c37383f0fb

[crypto] more moving to compiler intrinsics

See ZX-1747

Technically this introduces a change in behavior. Before the code would
crash - now this error condition is handled gracefully.

Change-Id: Ie9a0bb65d830df581e6401a70b555c8eaca3afe9

[crypto][fdio][zxcrypt] Improve debug output

This CL improves fdio/debug's xprintf with location info.

Change-Id: Idd05c0439258ed3fe160086bcce05575eddbc38b

[crypto] Improve Bytes::Increment

This CL modifies Bytes::Increment to be incremented by a set amount
rather than just by 1. This is to enable better random access for
Ciphers with a tweaked codebook mode (next CL).

Change-Id: I62aec4c805f12c64b2df5f27bc8eb8346c4b99ec

[ulib/crypto] Bytes class improvements

This CL adds a few more helper methods and tweaks to Bytes:
- Copy(const Bytes &) copies from another Bytes object.
- Resize(size_t) is a no-op if the size is unchanged.
- Randomize(0) will skip the resizing step.
- Merge(const Bytes &) copies another Bytes to the end of this one.
- Split(Bytes*) copies to another Bytes from the end of this one.

Change-Id: I9fced1b700285b51e8e8461472cf5ee6dccb5640

[crypto] Add Bytes::Increment.

This CL adds a method to Bytes to treat its contents as an arbitrary
precision unsigned integer to be incremented.

Change-Id: Ief385c9fa930451036df6b208f6710406e893573

[crypto] Add Bytes class

This CL adds Bytes, which represents a byte buffer with methods to
securely erase on destruction and compare in constant time.

Change-Id: I2c970d02eb70c09c59c76d7c5640a14b02c23d68