[BUGFIX] SIG_ALL check returns true for other sigflags

[lollerfirst]

Return true in a SIG_ALL check if no inputs contain SIG_ALL sigflags.
This prevents an early P2PK check in melt from wrongfully rejecting P2PK locked secrets that only have SIG_INPUTS sigflags.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.85%. Comparing base (3e32dc4) to head (12604be).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #767      +/-   ##
==========================================
+ Coverage   55.36%   60.85%   +5.48%     
==========================================
  Files          84       89       +5     
  Lines        9479    10529    +1050     
==========================================
+ Hits         5248     6407    +1159     
+ Misses       4231     4122     -109     

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[callebtc]

LGTM