feat(BUX-177): prepare beef hex

[arkadiuszos4chain]

Prepare a BEEF transaction for a P2P receiver who can handle it.
Works only if all inputs come from mined transactions.

[codecov]

Codecov Report

Merging #395 (978ef79) into master (987f698) will decrease coverage by 0.39%.
The diff coverage is 26.88%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #395      +/-   ##
==========================================
- Coverage   51.96%   51.57%   -0.39%     
==========================================
  Files          92       95       +3     
  Lines       10683    10872     +189     
==========================================
+ Hits         5551     5607      +56     
- Misses       4698     4831     +133     
  Partials      434      434              

Flag	Coverage Δ
unittests	51.57% <26.88%> (-0.39%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
beef_tx.go	0.00% <0.00%> (ø)
beef_tx_bytes.go	0.00% <0.00%> (ø)
model_sync_transactions.go	21.07% <0.00%> (+0.19%)	⬆️
model_transaction_config.go	80.98% <0.00%> (-2.55%)	⬇️
paymail.go	55.17% <0.00%> (-5.44%)	⬇️
utils/utils.go	82.60% <0.00%> (-10.08%)	⬇️
model_compound_merkle_path.go	65.51% <25.00%> (-6.86%)	⬇️
beef_tx_sorting.go	100.00% <100.00%> (ø)

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[mrz1836]

LGTM