perf: use fmt.Fprintf to avoid unnecessary string+args + WriteString

[odeke-em]

In a bid to remove unnecessary CPU and memory bloat for the gnovm which takes the order of minutes to run certain code, I noticed the pattern:

io.StringWriter.WriteString(fmt.Sprintf(...))

in which fmt.Sprintf(...) has to create a string by inserting all arguments into the format specifiers then pass that into .WriteString which defeats the entire purpose of io.StringWriter.WriteString that *bytes.Buffer and *strings.Builder implement.

Just from picking a single benchmark that already exists results in improvements in all dimensions:

name               old time/op    new time/op    delta
StringLargeData-8    8.87ms ± 1%    8.28ms ± 3%   -6.68%  (p=0.000 n=17+19)

name               old alloc/op   new alloc/op   delta
StringLargeData-8    8.44MB ± 0%    7.78MB ± 0%   -7.75%  (p=0.000 n=20+19)

name               old allocs/op  new allocs/op  delta
StringLargeData-8     94.1k ± 0%     70.1k ± 0%  -25.51%  (p=0.000 n=15+20)

for heavily used code this is going to reduce on garbage collection cycles too.

Fixes #3433

[Gno2D2]

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Codecov Report

Attention: Patch coverage is 90.62500% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
gnovm/pkg/gnolang/machine.go	85.71%	3 Missing ⚠️

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[notJoon]

more cleaner than previous version. I left some comments

[odeke-em]

Thank you for the code review and discourse @notJoon, I've made an update, kindly please help me take another stab.

[notJoon]

LGTM 💯

[n2p5]

Reviewed over video call with @odeke-em , LGTM.

[n2p5]

I gave feedback to @odeke-em out-of-band. He's going to sort out the last of the failing tests and we can merge.