src: check import attributes value types as strings

[legendecas]

Import attribute key and value only support literal string values. Add DCHECKs to ensure that the types are expected.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders
• @nodejs/vm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.06%. Comparing base (f5da8f8) to head (d1941fc).
Report is 14 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58986      +/-   ##
==========================================
- Coverage   90.08%   90.06%   -0.03%     
==========================================
  Files         640      641       +1     
  Lines      188517   188668     +151     
  Branches    36975    37005      +30     
==========================================
+ Hits       169826   169924      +98     
- Misses      11402    11449      +47     
- Partials     7289     7295       +6     

Files with missing lines	Coverage Δ
src/module_wrap.cc	73.22% <100.00%> (+0.06%)	⬆️

... and 39 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67885/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67887/