MFV: zstd 1.5.2

Merge commit 'b3392d84da5bf2162baf937c77e0557f3fd8a52b' into zstd_1.5.2

full changelog: https://github.com/facebook/zstd/compare/v1.4.8...v1.5.2

Updated sys/kern/subr_compressor.c to new API

MFC after: 3 days
Relnotes: yes
Sponsored by: Klara, Inc.

Update to Zstandard 1.4.5

As usual, the full release notes are found on Github:

https://github.com/facebook/zstd/releases/tag/v1.4.5

Notable changes include:

* Improved decompress performance on amd64 and arm (5-10%
and 15-50%, respectively).
* '--patch-from' zstd(1) CLI option, which provides something like a very fast
version of bspatch(1) with slightly worse compression. See release notes.

In this update, I dropped the 3-year old -O0 workaround for an LLVM ARM bug;
the bug was fixed in LLVM SVN in 2017, but we didn't remove this workaround
from our tree until now.

MFC after: I won't, but feel free
Relnotes: yes

Update to Zstandard 1.4.4

The full release notes can be found on Github:

https://github.com/facebook/zstd/releases/tag/v1.4.4

Notable changes in this release include improved decompression speed (about
10%). See the Github release notes for more details.

MFC after: I'm not going to, but feel free
Relnotes: yes

Update to Zstandard 1.4.0

The full release notes can be found on Github:

https://github.com/facebook/zstd/releases/tag/v1.4.0

Relnotes: yes

Move zstd from contrib to sys/contrib so it can be used in the
kernel. Adjust the Makefiles that referenced it to the new path.

Sponsored by: Netflix
OK'd by: cem@ and AllanJude@

Move zstd from contrib to sys/contrib so it can be used in the
kernel. Adjust the Makefiles that referenced it to the new path.

Sponsored by: Netflix
OK'd by: cem@ and AllanJude@