feat(gnodev): allow gnodev to load txs

[deelawn]

This is useful for testing an app; it allows gnodev to be started each time with a particular state -- the result of the provided transactions.

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
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

Attention: Patch coverage is 4.65116% with 41 lines in your changes missing coverage. Please review.

Project coverage is 54.59%. Comparing base (7bced19) to head (24dd185).

Files	Patch %	Lines
tm2/pkg/std/tx.go	0.00%	21 Missing ⚠️
contribs/gnodev/cmd/gnodev/txs.go	0.00%	8 Missing ⚠️
contribs/gnodev/cmd/gnodev/main.go	0.00%	6 Missing ⚠️
contribs/gnodev/cmd/gnodev/setup_node.go	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2281      +/-   ##
==========================================
- Coverage   54.63%   54.59%   -0.04%     
==========================================
  Files         578      579       +1     
  Lines       77877    77896      +19     
==========================================
- Hits        42547    42531      -16     
- Misses      32159    32195      +36     
+ Partials     3171     3170       -1     

Flag	Coverage Δ
contribs/gnodev	23.96% <4.76%> (-0.29%)	⬇️
contribs/gnofaucet	15.31% <ø> (+0.85%)	⬆️
contribs/gnokeykc	0.00% <ø> (ø)
contribs/gnomd	0.00% <ø> (ø)
gno.land	61.62% <100.00%> (-0.03%)	⬇️
tm2	54.46% <0.00%> (-0.04%)	⬇️

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