Move forwarding_fee_proportional_millionths, forwarding_fee_base_msat to ChannelHandshakeConfig

[matchacactus]

First step for #216

[matchacactus]

The second commit broke test_priv_forwarding_rejection randomly. I have tried and failed to find out why, another 👀 for debug help?

[codecov-commenter]

Codecov Report

Merging #1247 (6bccdaa) into main (34cdca9) will increase coverage by 0.01%.
The diff coverage is 92.00%.

❗ Current head 6bccdaa differs from pull request most recent head c49c086. Consider uploading reports for the commit c49c086 to get more accurate results

@@            Coverage Diff             @@
##             main    #1247      +/-   ##
==========================================
+ Coverage   90.40%   90.42%   +0.01%     
==========================================
  Files          70       70              
  Lines       38087    38098      +11     
==========================================
+ Hits        34434    34449      +15     
+ Misses       3653     3649       -4     

Impacted Files	Coverage Δ
lightning/src/ln/functional_test_utils.rs	95.28% <ø> (ø)
lightning/src/util/config.rs	47.82% <0.00%> (+2.17%)	⬆️
lightning/src/ln/channel.rs	89.44% <100.00%> (+0.06%)	⬆️
lightning/src/ln/functional_tests.rs	97.28% <100.00%> (+0.01%)	⬆️
lightning/src/ln/onion_route_tests.rs	96.69% <100.00%> (ø)
lightning/src/ln/payment_tests.rs	99.14% <100.00%> (ø)
lightning/src/util/events.rs	32.73% <0.00%> (+0.35%)	⬆️

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[TheBlueMatt]

I'm somewhat confused as to the motivation for this PR - ChannelHandshakeConfig is all configuration options which are set at the beginning of a channel and then can not be changed afterwards - its all stuff in the "handshake". Instead, I think we should move things from ChannelConfig which cannot be updated after the handshake, specifically announced_channel (cannot be updated per lightning spec), commit_upfront_shutdown_pubkey (its literally about whether we include the pubkey in the handshake or not).

[TheBlueMatt]

Note that we cannot remove required elements, as old clients will refuse to load data serialized by new clients (which we guarantee won't happen at least across a few releases). We instead need to write the default value with something like (0, Some(DEFAULT_VALUE as u64), option)

[matchacactus]

I'm somewhat confused as to the motivation for this PR - ChannelHandshakeConfig is all configuration options which are set at the beginning of a channel and then can not be changed afterwards - its all stuff in the "handshake". Instead, I think we should move things from ChannelConfig which cannot be updated after the handshake, specifically announced_channel (cannot be updated per lightning spec), commit_upfront_shutdown_pubkey (its literally about whether we include the pubkey in the handshake or not).

I misunderstood the issue - am I on the right track with #1270? Closing this PR in favor of #1270

[TheBlueMatt]

Eventually landed rebased as #1529.