RLS: 3.1

[mroeschke]

TODOs:

• TRACKER: support for Python 3.15 #66740
• API: default to microseconds for Timestamp/Timedelta creation from numeric input #63275

Nice to have's

• TRACKER: support for Python 3.15 #66740 read_feather adaptation to pyarrow deprecation DEPR: read_feather #66177 (partially allow deprecation message)
• REF: Use moments accumulator from libalgos to compute variance #66302

[jbrockmendel]

1. I just finished having fable audit everything i've done since 3.0, have a handful of follow-ups to do this week.
   2)PERF: default read_csv parallel workers to available physical cores #66152 id like to discuss and ideally get in Punting to 3.1
2. I'd like to get Alvaro's simd reductions in, but not a blocker