GenType: ensure JS import works regardless moduleResolution

[cometkim]

As I and @fhammerschmidt discussed in fhammerschmidt/rescript-lang.org#1

This is a necessary change as we want to use the .res.js suffix instead of .bs.js. This is because import './Module.res' will be resolved as the original ReScript file instead of the generated Module.res.js file.

In #6182, I differentiated the case when moduleResolution: node to minimize output changes, but in fact, it is preferable always to use the full path if possible.

I added ModuleResolution1.res and ModuleResolution2.res tests to ensure that the moduleResolution option still applies to type import. But as they are always type-only modules since v11, the moduleResolution option doesn't make much sense anymore. This option should be removed again after the breaking change in #6196.

[cristianoc]

Are there any consequences to existing projects?
Eg the way bundlers work: does this change affect the results in some cases?

[cometkim]

This fixes cases where .res.js suffix could not be used due to the resolution issue, or cases where a custom rule had to be added to the bundler configuration.