[feature]: don't use/block `HtlcInterceptor` when running in standalone mode

[guggero]

Today (until lightningnetwork/lnd#7162 is addressed), lnd's HtlcInterceptor only allows a single RPC client to be connected at any time.

tapd's OrderHandler "consumes" that single slot on startup, making it impossible for other user apps to use the HtlcInterceptor.

We should allow the RFQ functionality to be turned off if tapd isn't running as part of litd in integrated mode and Taproot Asset Channel functionality is not available anyway, so the HtlcInterceptor can be freed up.

Ideally, of course, this falls away if lightningnetwork/lnd#7162 is addressed first.