fix: don't skip resolving files imported by other plugins

[agilgur5]

Summary

Resolve files imported from non-TS files / other plugins / JS files, such as TS files imported by Svelte files

• Fixes Rollup error Could not resolve TS files without extension (.ts) from Svelte files #283

Details

• previously the allImportedFiles Set was basically used to skip any files that were imported by other plugins

  • it only filtered out on importer (not importee)
  • this is a bit of a problem though, as other plugins that create JS code, or allowJs JS code, or heck, even regular JS code that Rollup processes without plugins, may actually import TS files
    • and Rollup's plugin system is designed to handle that scenario, so rpt2 actually should resolve those files
      • notably, rpt2 already transforms those files, it just didn't resolve them
        • which is why using @rollup/plugin-node-resolve with a .ts extension solved this as a workaround
          • the file would be resolved by node-resolve then actually transformed by rpt2
          • but rpt2 should resolve TS files itself, node-resolve shouldn't be necessary
    • this caused the issue that extensionless imports from such files wouldn't get resolved to TS files and may cause Rollup to error
      • in particular, this popped up with extensionless imports of TS files from Svelte files in Rollup error Could not resolve TS files without extension (.ts) from Svelte files #283

• resolveId is actually the last remaining place where allImportedFiles was used

  • so after removing it from here, we can just remove it entirely
    • which should be a small optimization

• for reference, allImportedFiles would be any included files as well as TS files that have been transformed (at this point in the build) and their references

  • this is a pretty gigantic list as is, so I'm actually not sure that removing this is actually that big of a de-opt
    • and it only affects mixed TS / non-TS codebases too

Historical Context

• this seems to have been added in b0a0ecb, but that commit doesn't actually seem to fix the issue it references, Plugin not respecting include / exclude when generating declarations #162
  • see my root cause analyses in fix: filter "missed" declarations as well #347 (comment) and Rollup error Could not resolve TS files without extension (.ts) from Svelte files #283 (comment) and my next comments after both of those
    • it took me a good bit of head-scratching to just realize this code seems to have been erroneous -- don't normally assume that code for a fix didn't actually solve the problem, nor that a regression can stay around for this long 😅 😕
      • I guess this is just an even bigger point for why solid testing is essential to keeping regressions and bugs out