[Very Slowly] Start Moving to inline format args

[TheBlueMatt]

In e2a05a4 we started ignoring
clippy's uninlined-format-args, but that doesn't mean that clippy
is wrong. Here we take the opportunity while doing cleanups to
search+replace a common string in channelmanager.rs which could
use inlined format arguments.

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[codecov]

Codecov Report

❌ Patch coverage is 39.02439% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.93%. Comparing base (ed42300) to head (1e0b75e).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/channelmanager.rs	39.02%	24 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3965      +/-   ##
==========================================
- Coverage   88.94%   88.93%   -0.01%     
==========================================
  Files         173      174       +1     
  Lines      123876   123869       -7     
  Branches   123876   123869       -7     
==========================================
- Hits       110177   110161      -16     
- Misses      11248    11256       +8     
- Partials     2451     2452       +1     

Flag	Coverage Δ
fuzzing	22.18% <0.00%> (+<0.01%)	⬆️
tests	88.76% <39.02%> (-0.01%)	⬇️

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[tnull]

This needs a run of rustfmt:

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 7fe43b915..2214676ce 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -6045,7 +6045,9 @@ where
                                        if let Some(funded_chan) = chan.as_funded() {
                                                if !funded_chan.context.is_usable() {
                                                        return Err(APIError::ChannelUnavailable {
-                                                               err: format!("Channel with id {next_hop_channel_id} not fully established"),
+                                                               err: format!(
+                                                                       "Channel with id {next_hop_channel_id} not fully established"
+                                                               ),
                                                        });
                                                }
                                                funded_chan

Otherwise LGTM

[tnull]

This needs a run of rustfmt:

Nevermind, seems I was looking at the branch before the latest force-push.

[tnull]

LGTM, will land, as it's trivial.