Bug/issue 820 deeply relative ESM paths in node modules not working

[thescientist13]

Related Issue

resolves #820

Summary of Changes

1. Refactored out usages of .replace('./', '') with custom functionality to better handle ./ vs ../ using @stencil/core for validation
2. Added tests and did some minor refactoring / commenting including not running walkModule on packages that already provide an exports map
3. Cleaning up import map snapshot to remove false positive entries

TODO

1. Sanity test first pass in downstream projects
2. Test with @stencil/core for handling ../ paths
3. Fix windows build - lol, I was way overthinking it. I was just about forcing windows path separators (\) to ESM style (/)
   • some sort of race condition it seems. Looks like the right path from the export map on Windows is being overwritten (?) later on by further calls to updateImportMap from walking the imports of a related @babel/runtime file? Was able to reproduce the same error on macOS by removing this one-off pre-check, so seems like the issue is somewhere in there 🔬 👀
4. Final sanity test again in downstream projects
   • https://github.com/thegreenhouseio/www.thegreenhouse.io
   • [WIP] examples of using Lion components greenwood-getting-started#45
   • [WIP] example with Material Web Components greenwood-getting-started#42
   • https://github.com/ContributaryCommunity/www.contributary.community
5. Misc TODOs / comment cleanup - deferred to leverage import.meta.resolve to support import maps generation and accurate node_modules resolution when building #684
6. (stretch) Test with @stencil/core for handling assumed barrel paths (files that assume resolving to a root level index.js via bare specifier (likely will make its own issue as it is a lower priority) - tracked in auto-resolve dependencies that only import from a directory #907