chore(gnovm): prevent assignment to non-assignable expressions

[omarsy]

closes: #2889

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[bot]]

Codecov Report

Attention: Patch coverage is 92.85714% with 2 lines in your changes missing coverage. Please review.

Project coverage is 63.12%. Comparing base (af05780) to head (fbc3bbe). Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
gnovm/pkg/gnolang/type_check.go	92.00%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2896      +/-   ##
==========================================
- Coverage   63.32%   63.12%   -0.21%     
==========================================
  Files         548      548              
  Lines       78511    80213    +1702     
==========================================
+ Hits        49719    50636     +917     
- Misses      25438    26171     +733     
- Partials     3354     3406      +52     

Flag	Coverage Δ
contribs/gnodev	60.57% <ø> (ø)
contribs/gnofaucet	15.77% <ø> (+0.94%)	:arrow_up:
gno.land	67.18% <ø> (ø)
gnovm	67.90% <92.85%> (+0.02%)	:arrow_up:
misc/genstd	79.72% <ø> (ø)
tm2	62.37% <ø> (-0.05%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[ltzmaxwell]

should share some logic with this: https://github.com/gnolang/gno/issues/1946