fix(@angular/build): link partial Ivy dependencies in Vitest runner

[alan-agius4]

Closes #34198

[gemini-code-assist]

Code Review

This pull request integrates the Angular linker into the Vitest unit test runner by utilizing JavaScriptTransformer to link partially-compiled packages. It also configures dependency optimization using browser targets and adds a behavior test to verify the linking process. The review feedback suggests optimizing the angular:linker plugin by using the existing textDecoder to decode transformed data instead of creating a temporary Buffer instance.

[gemini-code-assist]

Since textDecoder is already instantiated at the module level (line 323), we can use it here to decode transformedData instead of creating a temporary Node.js Buffer instance. This is more consistent with the rest of the file and avoids unnecessary buffer allocations.

Suggested change

	const transformedData = await prebundleTransformer.transformData(id, code);
	return Buffer.from(transformedData).toString('utf-8');
	const transformedData = await prebundleTransformer.transformData(id, code);
	return textDecoder.decode(transformedData);