Add Utxo::new_v1_p2tr

[wvanlint]

This PR adds a method to create a Utxo for a SegWit v1 P2TR output, resolving a TODO in ldk-sample: https://github.com/lightningdevkit/ldk-sample/blob/6c300c7b744eddf8e3c5a3336f7c19110b9dab4e/src/bitcoind_client.rs#L431.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.99%. Comparing base (44b9529) to head (404ead6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4365   +/-   ##
=======================================
  Coverage   85.98%   85.99%           
=======================================
  Files         156      156           
  Lines      102605   102629   +24     
  Branches   102605   102629   +24     
=======================================
+ Hits        88229    88258   +29     
+ Misses      11867    11864    -3     
+ Partials     2509     2507    -2     

Flag	Coverage Δ
tests	85.99% <100.00%> (+<0.01%)	⬆️

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[ldk-reviews-bot]

🔔 1st Reminder

Hey @wpaulino! This PR has been waiting for your review.
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[TheBlueMatt]

Thanks! one doc nit otherwise LGTM

[TheBlueMatt]

Should this specify that we mean a keypath spend specifically?