## Description

This improves defaults generation with logging, stats, and token validation. 

This PR includes these changes:
* introduce `TokenLogger`, with a verbose mode
  * prints versions and tokens usage to the console
  * outputs `generated/used_tokens.csv`, a list of all used tokens, for use by Google
* find token files in `data` automatically
* hide tokens `Map`
  * tokens can be obtained using existing resolvers (e.g. `color`, `shape`), or directly through `getToken`.
  * tokens can be checked for existence with `tokenAvailable`
* remove version from template, since the tokens are aggregated and multiple versions are possible (as is the case currently), it does not make sense to attribute a single version
* improve documentation

## Related Issues
 - Fixes https://github.com/flutter/flutter/issues/122602

## Tests
 - Added tests for `TokenLogger`
 - Regenerated tokens, no-op except version removal

## Future work
A future PR should replace or remove the following invalid tokens usages

<img width="578" alt="image" src="https://github.com/flutter/flutter/assets/6655696/b6f9e5a7-523f-4f72-94f9-1b0bf4cc9f00">