feat: scan memory, reset allocator

[petar-dambovaliev]

This is as an alternative solution to garbage collection to reclaim memory.
If an allocation is about to fail, walk all blocks in the machine and their values and recalculate how much memory is used.

[codecov]

Codecov Report

Attention: Patch coverage is 10.63830% with 42 lines in your changes missing coverage. Please review.

Project coverage is 63.76%. Comparing base (0246761) to head (4c5fcfd).

Files with missing lines	Patch %	Lines
gnovm/pkg/gnolang/alloc.go	2.50%	38 Missing and 1 partial ⚠️
gnovm/pkg/gnolang/machine.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3148      +/-   ##
==========================================
- Coverage   63.80%   63.76%   -0.04%     
==========================================
  Files         549      549              
  Lines       78833    78877      +44     
==========================================
- Hits        50300    50298       -2     
- Misses      25144    25188      +44     
- Partials     3389     3391       +2     

Flag	Coverage Δ
contribs/gnodev	61.16% <ø> (ø)
contribs/gnofaucet	14.82% <ø> (-0.95%)	⬇️
gnovm	67.86% <10.63%> (-0.09%)	⬇️
misc/genstd	79.72% <ø> (ø)
tm2	62.42% <ø> (-0.01%)	⬇️

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