Add BLAKE3 and xxHash (XXH3/XXH3-64 and XXH128/XXH3-128)

[albertony]

What is the purpose of this change?

Add support for BLAKE3 and xxHash (XXH3/XXH3-64 and XXH128/XXH3-128).

• Added to the rclone's hash library, with internal names: blake3, xxh3 and xxh128.
• Implicitly supported in rclone hashsum command.
• Implicitly supported by the local backend.
• Added local backend option --hashes to configure which hashes it should support.
  • E.g. :local,hashes=blake3:C:\Temp.
  • This can be used to test hashing performance of the different types of hashes, e.g. with local-to-local operations.
    • Because the default, as before, is for it to support all that rclone's hash library supports, and when needing one it picks the first of a the internally ordered list, currently md5, and with operations between two backends it will pick the first in common. For local-local operations this means it will always use md5.
• BLAKE3 support in SFTP backend.
  • Probes for blake3sum executable, or rclone hashsum blake3, configurable with blake3sum_command.

To experiment, beta builds are here: https://beta.rclone.org/branch/add-xxh-blake-hash/

TODO:

• Name and type (e.g. repeated parameter vs comma-separated value) of the local backend option, and general consistency of options to specify hash types:
  • Name of the new local backend option introduced here is currently hashes, and it takes a comma-separated list.
  • The hasher backend already has a similar option, with same name hashes, and also takes a comma-separated list.
  • The lsjson command has option hash to enable hash in output and hash-type option, which can be repeated, to specify which ones.
  • The lsf command has option hash to specify which hash to use option format is used with keyword "h".

• I have a slight concern about sftp startup times. Lots of people use sftp without a config file which means that it probes for shells/supported hashes each time it is used. Perhaps we should delay hash support probing until it is asked for?
  Support blake3 / b3sum as hash #7765 (comment)

Was the change discussed in an issue or in the forum before?

#7765 and https://forum.rclone.org/t/faster-non-cryptographic-hashing-algorithm-for-faster-file-comparison/23601

Checklist

• I have read the contribution guidelines.
• I have added tests for all changes in this PR if appropriate.
• I have added documentation for the changes if appropriate.
• All commit messages are in house style.
• I'm done, this Pull Request is ready for review :-)