feat(coverage): Add back coverage support for txtar

[gfanton]

Add back coverage support for txtar, which was removed during the CI rework.
This only includes txtar test files from gnovm package (not those for gnoland, I will do that in another PR).
It adds approximately 5% coverage, which is a non-negligible.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 60.11%. Comparing base (0e3c050) to head (cf276f1).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2377      +/-   ##
==========================================
+ Coverage   54.99%   60.11%   +5.11%     
==========================================
  Files         595      560      -35     
  Lines       79775    74686    -5089     
==========================================
+ Hits        43872    44895    +1023     
+ Misses      32581    26400    -6181     
- Partials     3322     3391      +69     

Flag	Coverage Δ
contribs/gnodev	60.58% <ø> (+34.58%)	⬆️
contribs/gnofaucet	14.46% <ø> (ø)
gno.land	64.15% <ø> (ø)
gnovm	64.18% <ø> (+3.97%)	⬆️
misc/genstd	80.54% <ø> (ø)
misc/logos	20.23% <ø> (+2.85%)	⬆️
tm2	62.05% <ø> (+7.55%)	⬆️

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[ajnavarro]

It looks like gnovm coverage went down 20%, we have to check why.

[gfanton]

I don't think we actually lost coverage. I believe the reason why the gnovm flag coverage is decreasing by 20% is because enabling coverage on txtar also generates coverage for tm2 packages. Therefore, the gnovm directory itself has not lost coverage. However, by including tm2 packages in the gnovm flags, we cover 20% less than gnovm packages only.

Coverage with gnovm flags including txtar (from gnovm/cmd/gno):

Coverage with gnovm flags excluding txtar (from gnovm/cmd/gno):

[gfanton]

@ajnavarro An idea to avoid having gnovm flags "corrupted" by txtar coverage, is to put txtar coverage under its own flag, such as gnovm/txtar.

[gfanton]

@ajnavarro should be good now

[ajnavarro]

IMO having txtar on its own coverage tag does not makes sense... A tag is defined per module we are testing, not by a group of tests...

What is specifically testing txtar? gnovm? tm2? gno node? a mix?
If we have a mix of tests testing different modules we should split them to be on these modules, if not it might be eventually a nightmare.

[gfanton]

i've added filtering by module so it doesn't expand coverage on multiple tags