Formalise `Compliant*` protocols

[dangotbanned]

Probably should've opened this sooner to track existing efforts, but better late than never.

Tasks

• refactor: adds _Stores(Native|Compliant) #2130
  • chore: Add CompliantDataFrame.native #2249
  • chore: Update ._native_frame refs #2290
  • chore: Update ._native_series refs #2293
  • chore: Add EagerSeries*Namespace protocols #2294
• refactor: adds _compliant sub-package #2149
• refactor: Generic CompliantSelector #2064
• feat: Spec'd-out CompliantExpr #2119
• chore(typing): Fill out CompliantNamespace protocol #2202
• chore: Spec CompliantDataFrame #2223
  • chore(typing): add missing _FullContext to CompliantDataFrame #2251
• chore: Spec CompliantLazyFrame #2232
• chore: Spec CompliantSeries #2236
• feat: Adds CompliantGroupBy #2252
  • See ([surviving mutant] in groupby.agg (pyarrow) #2184 (comment))
• feat: Adds Compliant(When|Then) #2261

Related

• API: io functions for v2 #2116
• Commitment to keep package size down #1942
• Request for contributions: Ibis support #1886
• [Enh]: Support Daft DataFrame #2222