refactor(standards): split fee estimation out of pay_fee

[mmagician]

Summary

Port of #3784 from release/v0.16.0-rc to next.

Changes w.r.t. #3784

• Adapted to next: tx::get_fee_faucet_id became tx::get_fee_asset_id (#3741), which returns the asset ID directly, so the rc pay_network_note_sponsorships wrapper collapsed to a single call and was dropped as suggested in the rc review. fungible_asset::to_amount_unchecked follows the next rename.
• On refactor(standards): split fee estimation out of pay_fee #3784, fee asset ID was read twice. pay_fee called estimate_fee, which read tx::get_fee_faucet_id to run the estimate, and then called pay_network_note_sponsorships, which read it again to run the creation. On next, the port now reads tx::get_fee_asset_id once in pay_fee, duplicates the word on the stack, and passes one copy to estimate/create respectively.

Notes

The two follow-ups originally listed here (zero-priced network notes budgeted at the 512-cycle walk margin while the payment pass still priced them via FPI after compute_fee, and the double pricing pass adding about 3950 core rows to network-note transactions) are addressed by b0e0179: the estimate records each network note's price in pay_fee's local memory and the payment reads it back, so every network note is priced once and the payment tail no longer contains a foreign procedure call. "consume CLAIM note (L2 to Miden)" is back to 4378 rows under its 65536 bracket.