Add capability to check memory usage within the code

[Kouteki]

          If it's possible to pull various data from the `Machine`, how about creating a package like `runtime`? I think it would be useful if we could directly check the memory usage by using `Alloc` field including gas usage, within the code.

gno/gnovm/pkg/gnolang/alloc.go

Lines 9 to 12 in de2fc45

	type Allocator struct {
	maxBytes int64
	bytes int64
	}

Originally posted by @notJoon in #1998 (comment)

[thinhnx-var]

Can I assume that you suggests a feature that realm developers are able to check the amount that will be allocated in memory of the data, and how much it does cost in gas ? If I was right I will implement this feat as I am currently doing the GasUsed() funtions ✋
@notJoon

[notJoon]

Can I assume that you suggests a feature that realm developers are able to check the amount that will be allocated in memory of the data, and how much it does cost in gas ? If I was right I will implement this feat as I am currently doing the GasUsed() funtions ✋ @notJoon

Yes, I think it would be good to show them together because the gas usage has some correlation with memory usage and vice versa. However, my intention was to make the foundation for measuring code performence like Go's pprof and prove better metrics to optimize code efficiently. So in my opinion it would better to implement them individually.

[thinhnx-var]

Ok I understand your intention. I gonna implement this good idea within std package first.
Many thanks @notJoon