Template validation enhancement: Validate string names and values against the expected defaults

[baronfel]

Is your feature request related to a problem? Please describe.

In dotnet/aspire#3190 some template localization content got left behind because the string keys and values weren't kept in sync.

Describe the solution you'd like.

It would be good to have a test helper or build validation that verifies:

• all localization files have the same keys that are in the template.json file, and
• the localization values in one language (default en) match those in the template.json file

Additional context

No response