feat: add keyName to integrations

[wasabeef]

What does this change?

Fixes #322 #327 🎯

Change to asset.gen.dart same properties.

When package_parameter_enabled = true

String get path => _assetName;

String get keyName => 'packages/$packageName/\$_assetName';

When package_parameter_enabled = false

String get path => _assetName;

String get keyName => _assetName;

Type of change

Please delete options that are not relevant.

• New feature (BREAKING CHANGES)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

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  • Ensure the tests (melos unit:test-script)
  • Ensure the analyzer and formatter pass (melos run format to automatically apply formatting)
• Appropriate docs were updated (if necessary)