Rollup merge of #68127 - varkor:clarify-extended-option, r=alexcrichton

Rollup merge of #68127 - varkor:clarify-extended-option, r=alexcrichton

Clarify the relationship between `extended` and `tools` in `config.toml`

I.e. `tools` is only effective if `extended = true`. Alternatively, we could make `tools = []` by default and remove `extended` (although we'd want to list the possible options), but improving the description seems sufficient to solve the issue.

Fixes https://github.com/rust-lang/rust/issues/61194.