feat: (gnovm): garbage collection

[ltzmaxwell]

address: #266 .

When the allocator runs out of memory, it reports “allocation limit exceeded.” At this point, the garbage collector (GC) scans blocks and frames to identify objects that are still reachable from the machine. It then recalculates the memory they consume and resets the allocator accordingly.

When a block is popped or set to nil, all objects defined and allocated within it become unreachable and are no longer counted toward the allocation limit.

A simple gas consumption logic is implemented by counting the number of GC cycles, specifically tracking how many times Allocate is invoked. However, I believe a more precise approach should be determined through benchmarking, which can be expanded after.

[Gno2D2]

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Codecov Report

Attention: Patch coverage is 78.52761% with 70 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
gnovm/pkg/gnolang/gonative.go	21.87%	21 Missing and 4 partials ⚠️
gnovm/pkg/gnolang/alloc.go	86.23%	14 Missing and 5 partials ⚠️
gnovm/pkg/gnolang/values.go	70.31%	17 Missing and 2 partials ⚠️
gnovm/pkg/gnolang/uverse.go	71.42%	6 Missing ⚠️
gnovm/pkg/gnolang/realm.go	0.00%	1 Missing ⚠️

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