[feature]: allow configuring multiple price oracles

[ZZiigguurraatt]

We have the ability to set a single price oracle server in tapd.conf:

taproot-assets/sample-tapd.conf

Lines 358 to 361 in d81faf9

	; Price oracle gRPC server address (rfqrpc://<hostname>:<port>)
	; To use the integrated mock, use the following value:
	; use_mock_price_oracle_service_promise_to_not_use_on_mainnet
	; experimental.rfq.priceoracleaddress=

I'd like the ability to set multiple price oracle servers.

We should have the ability to set a primary and a backup global oracle that we trust for all assets

Or, we should be able to set a primary and backup oracle that is only valid for a specific asset id.