chore(firestore): rename named-db to enterprise

[wu-hui]

This PR renames the Firestore tests in the Node.js Server SDK to use the term 'enterprise' instead of 'named-db', aligning it with the naming conventions used in the other SDKs.

• Renamed environment variable FIRESTORE_NAMED_DATABASE to FIRESTORE_DATABASE_ID.
• Renamed npm scripts in package.json from system-test:named-db:... to system-test:enterprise:....
• Updated composite system test scripts to use the new enterprise names.
• Updated integration test source code to consume the new property.

[gemini-code-assist]

Code Review

This pull request renames the environment variable FIRESTORE_NAMED_DATABASE to FIRESTORE_DATABASE_ID across system tests and updates the corresponding script names in package.json. The review feedback recommends adding a fallback to the previous environment variable name in firestore.ts and tracing.ts to ensure backward compatibility for existing test setups.

[gemini-code-assist]

To avoid breaking existing test environments that rely on the previous environment variable name, consider adding a fallback to FIRESTORE_NAMED_DATABASE while transitioning to FIRESTORE_DATABASE_ID.

Suggested change

	if (process.env.FIRESTORE_DATABASE_ID) {
	internalSettings.databaseId = process.env.FIRESTORE_DATABASE_ID;
	const databaseId = process.env.FIRESTORE_DATABASE_ID || process.env.FIRESTORE_NAMED_DATABASE;
	if (databaseId) {
	internalSettings.databaseId = databaseId;
	}

[gemini-code-assist]

Similar to the change in firestore.ts, providing a fallback for the environment variable name ensures backward compatibility for existing test setups.

Suggested change

	if (process.env.FIRESTORE_DATABASE_ID) {
	settings.databaseId = process.env.FIRESTORE_DATABASE_ID;
	const databaseId = process.env.FIRESTORE_DATABASE_ID || process.env.FIRESTORE_NAMED_DATABASE;
	if (databaseId) {
	settings.databaseId = databaseId;
	}

[MarkDuckworth]

Thanks for standardizing the env variable