Mark ChannelManager::send_payment_with_route as deprecated and take Route by value

[TheBlueMatt]

We probably should have done this long ago a release or two after
adding send_payment, but we didn't and the second best time is
now.

send_payment_with_route has particularly hard to use retry
semantics that make it unsuitable for real use. Once we get the
last of our users off of it, we'll want to remove it (or at least
mark it test-only), but we should start by deprecating it.

Now that ChannelManager::send_payment_with_route is deprecated,
we don't care too much about making it as effecient as possible, so
there's not much cost to making it take Route by value. This
avoids bindings being unsure if the by-reference Route passed
needs to outlive the ChannelManager itself or if it only needs to
outlive the method call, creating some call overhead by forcing a
Route::clone, but avoiding a memory leak.

[codecov]

Codecov Report

Attention: Patch coverage is 99.35065% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.75%. Comparing base (8c1b3d1) to head (753a7ac).
Report is 12 commits behind head on main.

Files	Patch %	Lines
lightning/src/ln/functional_test_utils.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3224   +/-   ##
=======================================
  Coverage   89.75%   89.75%           
=======================================
  Files         122      122           
  Lines      101791   101791           
  Branches   101791   101791           
=======================================
+ Hits        91360    91362    +2     
+ Misses       7748     7746    -2     
  Partials     2683     2683           

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