npm-packlist gets normalized package-json when assessing files to include. when main is specified with relative file path it doesn't consider that entry when including files. Fixing main in normalization step

• check on changes condition
• sanity testing
• check npm pack command with empty files array in package.json
  • arborist node uses read-package-json-fast normalization functionality instead of package-json's normalization flow
• need to check for read-package-json-fast's normalization logic to replace it with package-json's normalization

Fixes: npm/cli#7799