Function listTestsetsAction

listTestsetsAction(): void
Lists all available testsets in the configuration. Shows testset names, number of tests, and groups.

Returns void
Resolves when listing completes
Throws
If Config.json is invalid or missing testsets
Example
```
// From CLI: polyman list testsets
await listTestsetsAction();
// Displays:
//   1. tests: 15 tests, groups: samples, main
//   2. stress: 100 tests, groups: none
```
- Defined in actions.ts:898