fix(gnolang): ensure complete Uverse initialization

[thehowl]

Fixes #2067.

UverseNode now distinguishes when it's uninitialized, initializing and initialized. In combination with calling Uverse() at init, we make sure that after package initialization we always have the same result from Uverse() and UverseNode() and we don't have issues like those pointed out in #2067.

[codecov]

Codecov Report

Attention: Patch coverage is 78.25261% with 229 lines in your changes missing coverage. Please review.

Project coverage is 63.40%. Comparing base (5c876f3) to head (cd46837).
Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
gnovm/tests/file.go	34.83%	51 Missing and 7 partials ⚠️
gnovm/pkg/gnolang/preprocess.go	93.17%	24 Missing and 10 partials ⚠️
gnovm/stdlibs/std/params.go	0.00%	34 Missing ⚠️
gnovm/pkg/gnolang/types.go	0.00%	15 Missing ⚠️
gnovm/pkg/gnolang/nodes_string.go	38.88%	10 Missing and 1 partial ⚠️
gnovm/pkg/gnolang/values.go	77.08%	9 Missing and 2 partials ⚠️
gnovm/pkg/gnolang/nodes.go	68.96%	5 Missing and 4 partials ⚠️
gnovm/pkg/gnolang/op_call.go	52.94%	6 Missing and 2 partials ⚠️
tm2/pkg/sdk/params/handler.go	81.57%	4 Missing and 3 partials ⚠️
tm2/pkg/sdk/params/keeper.go	91.66%	4 Missing and 2 partials ⚠️
... and 10 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2997      +/-   ##
==========================================
+ Coverage   63.18%   63.40%   +0.21%     
==========================================
  Files         561      565       +4     
  Lines       78636    79473     +837     
==========================================
+ Hits        49690    50389     +699     
- Misses      25569    25690     +121     
- Partials     3377     3394      +17     

Flag	Coverage Δ
contribs/gnodev	60.57% <ø> (+0.62%)	⬆️
contribs/gnofaucet	14.82% <ø> (ø)
gno.land	67.37% <70.83%> (-0.01%)	⬇️
gnovm	67.86% <76.74%> (+0.26%)	⬆️
misc/genstd	79.72% <ø> (ø)
tm2	62.48% <89.20%> (+0.16%)	⬆️

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[jefft0]

FYI, I tested and this fixes the "flappy" test reported in this comment.