[sBTC] Add stx_address method to PegOutRequestOp

[netrome]

This PR adds a PegOutRequestOp::stx_address() method to derive the stacks address of an sBTC holder requesting to peg out.

Closes #3647

[igorsyl]

@kantai I would be grateful for your attention to this PR given it's one of the last remaining pieces for a working sBTC Alpha.

[kantai]

This LGTM, but it needs two more kinds of tests:

1. A test that uses a test vector (i.e., just a hex encoded bitcoin transaction) as input, with a hard coded expected stx_address.
2. Test coverage for the two error cases

[netrome]

This LGTM, but it needs two more kinds of tests:

1. A test that uses a test vector (i.e., just a hex encoded bitcoin transaction) as input, with a hard coded expected `stx_address`.

2. Test coverage for the two error cases

Thank you for the feedback. I have added a test case with the test vector and another one for one of the error cases. I discovered that the other error case was infallible, so I changed the method and return type to reflect that.

It would be great if you could have another look @kantai 🙏

[codecov]

Codecov Report

Merging #3649 (5620634) into next (5ce2b54) will increase coverage by 2.11%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             next    #3649      +/-   ##
==========================================
+ Coverage   29.36%   31.47%   +2.11%     
==========================================
  Files         309      309              
  Lines      278266   278468     +202     
==========================================
+ Hits        81702    87661    +5959     
+ Misses     196564   190807    -5757     

Impacted Files	Coverage Δ
src/chainstate/burn/operations/peg_out_request.rs	13.21% <0.00%> (-9.21%)	⬇️

... and 91 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[kantai]

LGTM!

[igorsyl]

Thank you @kantai