stacked on top of #2020, merge 2020 first

• rent impl for c-PDA.

reuses most of the rent impl of c-token, however we always transfer rent to the program's rent_sponsor pda, even if a different fee_payer paid for rent exemption.

for a rent v1 the benefits of this (saves account space, simpler) outweigh the cons. I think thats fair because the "fee" goes to the program's rent_sponsor PDA, funding the next user's PDA rent exemption.

• added derive_rent_sponsor!(program_id) macro
• allow rust expressions as seeds to add_compressible_instructions!() macro
• allow seed references to other instruction accounts as well as instruction_data
• made macros modular, moved processors to token-sdk and sdk (compress_runtime.rs, decompress_runtime.rs)

added tests for the macros at every level:

• sdk-compressible-test is a manual implementation of the hooks
• csdk-anchor-derived-test uses most smaller macros
• csdk-anchor-full-derived-test uses add_compressible_instructions macro

Summary by CodeRabbit

• New Features

  • New compressible macros/derives and runtime processors for idempotent compression/decompression (PDAs & tokens).
  • RentSponsor type and rent-sponsor PDA derivation helpers.

• Documentation

  • Added comprehensive Compressible GUIDE and README with PDA-only, token, cToken, cMint, and client workflows.

• Improvements

  • Config extended with compression authority, rent settings, and write top-up; simplified per-account idempotent compression flow and safer edge-case handling (fewer required parameters).

_{✏️ Tip: You can customize this high-level summary in your review settings.}