chore: clean up the params keeper

[zivkovicmilos]

Description

This PR cleans up a bit the params keeper, and starts a discussion on some functionality that seems sketchy. It moves some testing code outside the binary, and into test files.

Additionally, I've updated some parsing methods so they're quicker now, by ~40ns:

goos: darwin
goarch: arm64
pkg: github.com/gnolang/gno/tm2/pkg/sdk/params
cpu: Apple M3 Max
BenchmarkParamsHandler_Query
BenchmarkParamsHandler_Query-14    	15104251	        79.11 ns/op
PASS

Before:

goos: darwin
goarch: arm64
pkg: github.com/gnolang/gno/tm2/pkg/sdk/params
cpu: Apple M3 Max
BenchmarkParamsHandler_Query
BenchmarkParamsHandler_Query-14    	 6789453	       156.6 ns/op
PASS

The keeper could probably be fully made generic, but for the sake of readability, this was not pursued.

cc @gfanton @moul

Topics that need discussing:

Internal funky returns

gno/tm2/pkg/sdk/params/keeper.go

Lines 118 to 128 in 4f27a57

	func (pk ParamsKeeper) getIfExists(ctx sdk.Context, key string, ptr interface{}) {
	stor := ctx.Store(pk.key)
	bz := stor.Get([]byte(key))
	if bz == nil {
	return
	}
	err := amino.UnmarshalJSON(bz, ptr)
	if err != nil {
	panic(err)
	}
	}

The method is called GetXXX, but it doesn't alter the pointer value internally if the value is missing.

Keeper (store) not being thread safe

The params keeper can be concurrently called, but it's not thread safe, actually. The underlying store is not thread safe

What if different modules concurrently call the keeper to store params?

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests

[codecov]

Codecov Report

Attention: Patch coverage is 84.66667% with 23 lines in your changes missing coverage. Please review.

Project coverage is 63.77%. Comparing base (38736e7) to head (1a5b33b).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
gno.land/pkg/sdk/vm/builtins.go	21.42%	8 Missing and 3 partials ⚠️
tm2/pkg/sdk/params/keeper.go	94.87%	3 Missing and 1 partial ⚠️
gno.land/pkg/gnoland/param.go	81.25%	2 Missing and 1 partial ⚠️
gno.land/pkg/sdk/vm/keeper.go	50.00%	2 Missing and 1 partial ⚠️
gno.land/pkg/gnoland/app.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3105      +/-   ##
==========================================
- Coverage   63.78%   63.77%   -0.02%     
==========================================
  Files         549      548       -1     
  Lines       78819    78839      +20     
==========================================
+ Hits        50275    50276       +1     
- Misses      25153    25167      +14     
- Partials     3391     3396       +5     

Flag	Coverage Δ
contribs/gnodev	60.54% <ø> (-0.63%)	⬇️
contribs/gnofaucet	15.77% <ø> (+0.94%)	⬆️
gno.land	73.48% <50.00%> (-0.23%)	⬇️
gnovm	67.93% <ø> (ø)
misc/genstd	79.72% <ø> (ø)
tm2	62.40% <96.42%> (+0.07%)	⬆️

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[zivkovicmilos]

@moul @gfanton
Ready for your eyes, I needed to get the expected functionality down after changes in #3003