services/horizon: add config setting for toggle soroban tx-meta presence

[sreuland]

What problem does your feature solve?

ability to control whether serialized tx meta for a soroban transaction is included in ingested transaction history

What would you like to see?

a new horizon config parameter ENABLE_SOROBAN_TXMETA_HISTORY, defaults to FALSE

when it's TRUE, and an incoming transaction is for soroban, the row for it in history_transactions table should have serialized base64 for an empty xdr.TransactionMetaV3{} intx_meta, and for the API resource model emitted for Transaction for this row needs to show the same value for
result_meta_xdr

also, confirm tx_sub doesn't leave anything around but still works for soroban tx's after this.

What alternatives are there?

this should target 2.28.0 release first, not master.

[sreuland]

closing, this was done in #5175 instead