Add last_local_balance_msats field

[Mirebella]

This PR adds last_local_balance_msats field. Solves #1898 .

I have a few open questions:

• what value should I assign to last_local_balance_msats, in file channel.rs at https://github.com/Mirebella/rust-lightning/blob/3eba0e2bbcb8547d561b175b1f19dd19565911b3/lightning/src/ln/channel.rs#L9591C1-L9591C33
• in mod.rs at https://github.com/Mirebella/rust-lightning/blob/3eba0e2bbcb8547d561b175b1f19dd19565911b3/lightning/src/events/mod.rs#L1538C6-L1538C44
  I saw that tlv fields are numbered differently(sometimes even numbers, sometimes odd numbers). I added my variable under number 11. Is that correct?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.62%. Comparing base (f7cc40e) to head (2557e6b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3235      +/-   ##
==========================================
- Coverage   89.63%   89.62%   -0.01%     
==========================================
  Files         126      126              
  Lines      102399   102408       +9     
  Branches   102399   102408       +9     
==========================================
+ Hits        91785    91786       +1     
- Misses       7888     7891       +3     
- Partials     2726     2731       +5     

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[Mirebella]

Does it look good?

[TheBlueMatt]

Basically looks good, just needs better docs.

[TheBlueMatt]

When you update the docs, please feel free to squash the commits down into one, but include more detail in the commit message - why was this change needed, what did the change do, any details about why the change was done in the way it was, etc.

[TheBlueMatt]

This basically LGTM, modulo the indentation note and the git commit message being missing. See https://cbea.ms/git-commit/ for a much, much, much longer discussion of how to write good commit messages.

[Mirebella]

Addressed all your points above, ready for review.

[TheBlueMatt]

Basicaly LGTM. Can you word-wrap your commit message so that no line is longer than ~70 chars? See-also https://cbea.ms/git-commit/ for commit message writing.

[TheBlueMatt]

nit, we usually tick our links so that they show up monospace

Suggested change

	/// For more accurate balances including fee information see [ChainMonitor::get_claimable_balances]
	/// For more accurate balances including fee information see [`ChainMonitor::get_claimable_balances`]

[vincenzopalazzo]

What Matt said regarding the commit, otherwise LGTM