Migrate to new reverse swap API

[ok300]

This is an umbrella issue for the entire migration.

• sdk: Introduce new API methods, deprecate existing
  • Add next-iteration reverse swap #816
  • Combine max_reverse_swap_amount and onchain_payment_limits #850
• sdk-doc: Update snippets to use new methods
  • Update docs to reflect reverse swap v2 breez-sdk-docs#140
• c-breez: Migrate to new methods
  • Use recommended fees when calculating claim tx feerates for reverse swap fee estimates c-breez#796
• sdk: Remove existing (old) reverse swap methods, models, bindings
  • Remove old (v1) reverse swap methods, models, bindings #922

Method changes:

• New methods:
  • onchain_payment_limits
  • prepare_onchain_payment
  • pay_onchain
  • in_progress_onchain_payments
• Deprecated:
  • max_reverse_swap_amount
  • fetch_reverse_swap_fees
  • send_onchain
  • in_progress_reverse_swaps

[ok300]

Tracking the future removal of v1 methods in #922.

All other points are addressed, so this can be closed as complete.