Use wyhash for <til/hash.h> (#13686)

wyhash was chosen based on the results found in `smhasher`, were it proved
itself as an algorithm with little flaws and fairly high output quality.

While I have a personal preference for xxhash (XXH3 specifically), wyhash is a
better fit for this project as its source code is multiple magnitudes smaller,
simplifying the review and integration into the header-only `hash.h` file.

For use with hashmaps the hash quality doesn't actually matter much for
optimal performance and instead the binary size usually matters more.
But even in that scenario wyhash is fairly close to FNV1a (aka "FNV64").

The result is that this new hash algorithm will only have little impact on
hashmap performance if used over the standard FNV1a as used in the STL,
while simultaneously offering a vastly better hash quality.

This partially solves #13124.

## Validation Steps Performed
* Added test cases ✅

oss/wyhash/LICENSE

@@ -0,0 +1,25 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <http://unlicense.org/>
+

oss/wyhash/MAINTAINER_README.md

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+### Notes for Future Maintainers
+
+[wyhash](https://github.com/wangyi-fudan/wyhash) is used as the hash algorithm for `<til/hash.h>` and its `til::hasher`.
+The source code was directly integrated into that header file and can be found in `/src/inc/til/hash.h`.

oss/wyhash/cgmanifest.json

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+{
+    "Registrations": [
+        {
+            "component": {
+                "type": "git",
+                "git": {
+                    "repositoryUrl": "https://github.com/wangyi-fudan/wyhash",
+                    "commitHash": "e77036ac1943369dc03e611cde52a8570f8ceefe"
+                }
+            }
+        }
+    ],
+    "Version": 1
+}