(cherry picked from commit e382abf)

(cherry picked from commit 0ff4f6d)

This PR adds the BLAKE3 C and asm sources to third_party, and includes a BUILD
file to build them.

PiperOrigin-RevId: 541539341
Change-Id: I49b1edce20a7d0f986e29712e6050e4e0b9c1d44

(cherry picked from commit a3a569e)

Support new-style digest functions.

This PR adds support for new-style digest functions to the remote execution
library code. The remote-apis spec says:

```
// * `digest_function` is a lowercase string form of a `DigestFunction.Value`
//   enum, indicating which digest function was used to compute `hash`. If the
//   digest function used is one of MD5, MURMUR3, SHA1, SHA256, SHA384, SHA512,
//   or VSO, this component MUST be omitted. In that case the server SHOULD
//   infer the digest function using the length of the `hash` and the digest
//   functions announced in the server's capabilities.
```

PiperOrigin-RevId: 543691155
Change-Id: If8c386d923db1b24dff6054c8ab3f783409b7f13

(cherry picked from commit 88412ce)

This PR adds the Blake3Hasher and Blake3HashFunction classes to vfs and
makes them available under the flag --digest_function=BLAKE3.

PiperOrigin-RevId: 550525978
Change-Id: Iedc0886c51755585d56b4d8f47676d3be5bbedba

(cherry picked from commit cc49d68)

Improve BLAKE3 performance by reducing copies.

Rather than buffering bytes, it's faster to just update the blake3 hasher as bytes are hashed.

Performance with buffering:
```
 Benchmark                   (inputSize)  Mode  Cnt      Score     Error  Units
 Blake3Benchmark.blake3Hash            1  avgt   10   1766.697 ± 709.515  ns/op
 Blake3Benchmark.blake3Hash           10  avgt   10   1466.253 ±  19.474  ns/op
 Blake3Benchmark.blake3Hash          100  avgt   10   1522.845 ±  15.480  ns/op
 Blake3Benchmark.blake3Hash         1000  avgt   10   2254.156 ±   8.588  ns/op
 Blake3Benchmark.blake3Hash        10000  avgt   10   4660.881 ±  28.637  ns/op
 Blake3Benchmark.blake3Hash       100000  avgt   10  24283.191 ±  32.754  ns/op
 Blake3Benchmark.sha256Hash            1  avgt   10    742.091 ±   6.307  ns/op
 Blake3Benchmark.sha256Hash           10  avgt   10    757.844 ±  12.042  ns/op
 Blake3Benchmark.sha256Hash          100  avgt   10    942.902 ± 555.874  ns/op
 Blake3Benchmark.sha256Hash         1000  avgt   10   1208.336 ± 508.392  ns/op
 Blake3Benchmark.sha256Hash        10000  avgt   10   4871.231 ± 494.507  ns/op
 Blake3Benchmark.sha256Hash       100000  avgt   10  40686.231 ±  63.814  ns/op
```

Performance without buffering (after this CL):

```
 Benchmark                   (inputSize)  Mode  Cnt      Score     Error  Units
 Blake3Benchmark.blake3Hash            1  avgt   10   1021.075 ±  11.640  ns/op
 Blake3Benchmark.blake3Hash           10  avgt   10   1029.561 ±  19.850  ns/op
 Blake3Benchmark.blake3Hash          100  avgt   10   1070.509 ±  12.140  ns/op
 Blake3Benchmark.blake3Hash         1000  avgt   10   1685.043 ±  13.963  ns/op
 Blake3Benchmark.blake3Hash        10000  avgt   10   3939.516 ±  13.212  ns/op
 Blake3Benchmark.blake3Hash       100000  avgt   10  21730.550 ±  22.976  ns/op
 Blake3Benchmark.sha256Hash            1  avgt   10    745.943 ±   9.853  ns/op
 Blake3Benchmark.sha256Hash           10  avgt   10    747.649 ±  17.381  ns/op
 Blake3Benchmark.sha256Hash          100  avgt   10    962.802 ± 590.879  ns/op
 Blake3Benchmark.sha256Hash         1000  avgt   10   1189.069 ± 412.327  ns/op
 Blake3Benchmark.sha256Hash        10000  avgt   10   4594.978 ±  21.833  ns/op
 Blake3Benchmark.sha256Hash       100000  avgt   10  39224.248 ± 229.265  ns/op
```

PiperOrigin-RevId: 551225043
Change-Id: I57dc0700b2f44d6faf75ffbd29f1607544e54f29

(cherry picked from commit d922ab3)

I noticed when testing the BLAKE3 digest function that uploaded files were being referenced incorrectly in the BES because they were missing the digest type. This CL fixes that.

Before: https://github.com/bazelbuild/bazel/assets/141737/52781f1b-b897-48f0-8956-f63c57b59436

After: https://github.com/bazelbuild/bazel/assets/141737/01ebc61b-3512-4ca5-8e2d-f47ad5f086b7

PiperOrigin-RevId: 553405394
Change-Id: Ic976e5a58f80ab8b5270b4aedc6204c22562533a

(cherry picked from commit 1929367)
Signed-off-by: Brentley Jones <github@brentleyjones.com>

DiskCache always stores files in /root/{cas/ac}/digestHash. This change keeps the current behavior, but for new style digest functions inserts a directory between /root/ and {cas/ac} to disambiguate the digest function type.

This prevents issues that could theoretically happen if there were hash collisions between two digest functions sharing the same cache directory.

PiperOrigin-RevId: 554477775
Change-Id: Ibef994e432764c260a3cab821ca6583c231c5b50

(cherry picked from commit f17b280)
Signed-off-by: Brentley Jones <github@brentleyjones.com>