Serialize blinded Trampoline hops

[arik-so]

Add BlindedForward and BlindedReceive variants to OutboundTrampolinePayload.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.94340% with 26 lines in your changes are missing coverage. Please review.

Project coverage is 90.17%. Comparing base (ac9a2c8) to head (67ecd63).
Report is 39 commits behind head on main.

Files	Patch %	Lines
lightning/src/ln/msgs.rs	50.94%	22 Missing and 4 partials ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3007      +/-   ##
==========================================
+ Coverage   89.42%   90.17%   +0.75%     
==========================================
  Files         117      118       +1     
  Lines       96290   104734    +8444     
  Branches    96290   104734    +8444     
==========================================
+ Hits        86109    94449    +8340     
- Misses       7962     8125     +163     
+ Partials     2219     2160      -59     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[TheBlueMatt]

Similarly, why is this draft? What's it waiting on?

[TheBlueMatt]

Can we get some docs, what does BlindedForward and BlindedReceive actually mean?