Refactor IndexedFrame.hash_values to use cudf::hashing functions, add xxhash64 to cudf Python.

[bdice]

Description

This PR refactors the Python code for IndexedFrame.hash_values to use the newer named C++ functions from cudf::hashing::*. I also added bindings for xxhash64 and updated some tests.

Needed for #14391.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[bdice]

Task list:

• Refactor Cython layer to align more closely with the C++ code (expose separate named functions, and dispatch at the Python layer) Punting on this until pylibcudf
• Add some regression tests for xxhash64. (There isn't a Python implementation of xxhash64 unless we want to add a new testing dependency -- I'd rather have regression tests than add a reference implementation.)

[bdice]

/merge