[v5] Replace CaseSensitivePathsPlugin with eslint import/no-unresolved rule

[raix]

Is your proposal related to a problem?

The CaseSensitivePathsPlugin is expensive, would be better for performance to use eslint rule https://github.com/import-js/eslint-plugin-import/blob/master/docs/rules/no-unresolved.md#casesensitive

referece: #11201 (comment)

Describe the solution you'd like

a2c859a

Describe alternatives you've considered

Additional context

#11201 (review)

[dantman]

This issue is part of the 5.0 milestone, suggesting it's blocking the release of CRA v5.

However investigating it it looks like CRA v4 also uses CaseSensitivePathsPlugin. So this is not a regression in the v5 alpha that needs fixing but a feature request.

If this isn't being worked on soon. Could this be moved to 5.x (or 6.0 if it's breaking)?