[feature]: Add Outgoing Custom TLVs to HTLC Interceptor

[carlaKC]

Is your feature request related to a problem? Please describe.

Users of the HTLC interceptor can receive custom records for the incoming HTLC, but do not have the ability to set custom records on the outgoing HTLC.

Describe the solution you'd like

Update the user-provided HTLCInterceptorResponse to allow interceptors to set CustomRecords for the outgoing HTLC.

Describe alternatives you've considered

There is no clear alternative other than upgrading the interceptor.

Additional context

This will be used to trial-run HTLC endorsement (and local reputation) as a mitigation for channel jamming attacks. Endorsement is a key part of this scheme, so propagation of this signal (using an experimental TLV) for testing purposes is important.

[carlaKC]

Fixed in #8660