fix(optimized_transaction): correct v0 signer ordering with separate fee payer

[pradhankukiran]

This fixes incorrect signer handling for versioned smart transactions when the fee payer differs from the provided signers.

Changes:

• build a canonical full signer set including the fee payer
• use VersionedTransaction::try_new(...) for signed v0 construction
• use the same full signer set for CU simulation
• add regression tests covering separate fee payer and out-of-order signer input

Root cause:

• the previous v0 path manually wrote signatures in caller order instead of message signer order
• CU simulation could also omit the fee payer when it was separate

Validation:

• cargo fmt --check
• cargo clippy -q
• cargo test -q

[0xIchigo]

Very nice! Thank you for the contribution! 🚀