services/horizon: Add the ability to toggle ingestion of Soroban elements

[sreuland]

What problem does your feature solve?

Some Change and Transaction processors in the ledger ingestion pipeline are parsing Soroban transaction metadata and are extracting data. These include, at minimum:

• the AssetStatsProcessor which extensively tracks changes to wrapped Stellar assets (see ingestAssetContractMetadata) - we discovered fundamental conflict here due to asset balances are based on trustlines/cb/lp entries which can also be changed by contracts and state verifier needs the contract tx-meta to re-assemble the full asset state value to compare against archive ledger entries of which trustlines/cb/lp include contract changes.
• the EffectProcessor which produces (account|contract)_(credited|debited) effects (see ingestEffects)
• 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
• 'asset_balance_changesindetailsof API Operation resource model, will be empty when Op is of type InvokeHostFunctionOp`, i.e. it wont parse contract events from tx meta to derive this in operations processor.

(We should take care to ensure the list above is complete, it may be non-exhaustive.)

These may incur significant increases in the compute time needed to finish ingesting a ledger when the Soroban transaction volume increases, and we need a way to disable this at runtime as a safety valve.

What would you like to see?

A new Horizon configuration setting, DISABLE_SOROBAN_INGEST_PROCESSORS, which defaults to FALSE. When it's TRUE, it will trigger specific routines in the aforementioned processors to skip Soroban-related parsing/extraction.

Note: This should target the v2.28.0 release first, not master.

What alternatives are there?

Wait for Horizon's ingestion time to blow up as Soroban resource limits increase.

[sreuland]

#5174 merged