Reserve bytes in anchor for the future new types and SPVs

[dr-orlovsky]

Required for enabling RGB-WG/RFC#3 in the future as a fast-forward and not a pushback

Related PRs:

• Move in ReservedBytes type from RGB Core LNP-BP/client_side_validation#161
• Move ReservedBytes to commit_verify crate RGB-WG/rgb-core#222

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 47.1%. Comparing base (78b23e3) to head (5d492b1).

Files	Patch %	Lines
dbc/src/anchor.rs	0.0%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master     #81     +/-   ##
========================================
- Coverage    47.2%   47.1%   -0.1%     
========================================
  Files          36      36             
  Lines        3216    3222      +6     
========================================
  Hits         1518    1518             
- Misses       1698    1704      +6     

Flag	Coverage Δ
rust	47.1% <0.0%> (-0.1%)	⬇️

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[zoedberg]

ACK 5d492b1