Allow plugins to be loaded from package subpaths #57266
                
     Merged
            
            
          
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Fixes #57047
When merged, this allows plugins to also be loaded from package subpaths.
Before,
tsconfig.json:compilerOptions.plugins[]would:package-plugin/sub/path@package-plugin/subpath..and.After,
tsconfig.json:compilerOptions.plugins[]will:package-plugin/sub/path@package-plugin/subpath@package-plugin/subpath/../../maliciousplugin/subpath/../../malicious..and.I noticed while looking at the tests that
.and..are accepted plugin names, which is likely unintentional.