[ecash-agora] Add ALP support to AgoraPartial.script

Summary:
Currently, AgoraPartial only supports SLP, with this diff it also supports ALP.

SLP and ALP have the same Agora Script except for the sub-script that builds the OP_RETURN output, as well as the last few ops.

ALP doesn't use the scriptSig to signal AGR0, instead it uses the OP_RETURN via eMPP. This increases tx size a bit, but simplifies usage significantly, as e.g. no ad setup tx is necessary anymore, and offers can be created directly in a single tx.

Depends on D16745.

Test Plan: npm test

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D16753