Add Signet support to non-liquidity service components of `litd`

[zoop-btc]

Is your feature request related to a problem? Please describe.
I'd love to use lightning terminal in my signet environment.

Describe the solution you'd like
Adding the signet network option in addition to mainnet, simnet, testnet & regtest.

Describe alternatives you've considered
No alternative.

Additional context
No additional context needed

Thank you and best regards,
Zoop

[MegalithicBTC]

Just pushing this up to see it's somehow been resolved but not noted in this issue. Using LND, we can use this configuration option:

bitcoin.signet=true

And then LND works well with Mutinynet (which is a signet).

Trying the same option in lit.conf ...
lnd.bitcoin.signet=true
... produces the error:

could not load config: ValidateConfig: The mainnet, testnet, regtest, simnet and signet params can't be used together -- choose one of the five

[dstadulis]

In situ code: All existing subserver daemons don't support signet.

There are two milestones needed to incorporating more signet support to litd

• Phase 0) Compile-time flag which adds support where any unsupported use of loop/pool just hard breaks
  • Intention is to deliver a demo-only binary that demo participants could use for tapd lightning functionality demos
• Phase 1) Support an "MVP-level" of signet support in litd.
  • Disable liquidity servicing products (loop, pool, etc) in litd-signet branch.
• Phase 2) A future edition of litd which has signet support for all daemons.

In an effort to expand testing for litd-experimental and to hasten the integration of taproot asset deployments, delivering Phase 1 will yield at a significant amount of testing while also not require major deployments loop, pool client nor server side code.

[dstadulis]

Issue fulfilled, given #902 merged