Move and Rustfmt channel acceptance and type downgrade tests

[carlaKC]

This PR moves tests related to channel acceptance / type downgrade into their own file (out of channelmanager) and formats them.

Depends on #3792 as requested in review.

[ldk-reviews-bot]

👋 I see @jkczyz was un-assigned.
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[codecov]

Codecov Report

Attention: Patch coverage is 97.59036% with 6 lines in your changes missing coverage. Please review.

Project coverage is 89.88%. Comparing base (0848e7a) to head (9388bba).

Files with missing lines	Patch %	Lines
lightning/src/ln/channel_acceptance_tests.rs	97.59%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3797   +/-   ##
=======================================
  Coverage   89.87%   89.88%           
=======================================
  Files         160      161    +1     
  Lines      129654   129700   +46     
  Branches   129654   129700   +46     
=======================================
+ Hits       116531   116579   +48     
- Misses      10428    10429    +1     
+ Partials     2695     2692    -3     

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[ldk-reviews-bot]

🔔 1st Reminder

Hey @jkczyz! This PR has been waiting for your review.
Please take a look when you have a chance. If you're unable to review, please let us know so we can find another reviewer.

[ldk-reviews-bot]

🔔 2nd Reminder

Hey @jkczyz! This PR has been waiting for your review.
Please take a look when you have a chance. If you're unable to review, please let us know so we can find another reviewer.

[carlaKC]

Removing bot-reviewer until dependent PR is in.

[ldk-reviews-bot]

✅ Added second reviewer: @wpaulino

[tankyleo]

A few more tests that caught my eye in channelmanager:

test_drop_disconnected_peers_when_removing_channels
test_drop_peers_when_removing_unfunded_channels
test_connection_limiting
test_outbound_chans_unlimited
test_0conf_limiting

What do you think ?

Otherwise, reproduced and matched everything so far on my machine.