Auto merge of #7918 - ehuss:features-doc-comment, r=Eh2406
Auto merge of #7918 - ehuss:features-doc-comment, r=Eh2406

Add extra details in the new feature resolver doc comment.

Some extra details about how the new feature resolver fits in the picture.

vojtechkral/cargo,rustyhorde/cargo,eminence/cargo,nipunn1313/cargo,rustyhorde/cargo,eminence/cargo,nipunn1313/cargo,vojtechkral/cargo,rust-lang/cargo,eminence/cargo,rustyhorde/cargo,tsurai/cargo,nipunn1313/cargo,tsurai/cargo,rust-lang/cargo,rust-lang/cargo,tshepang/cargo,tshepang/cargo,rustyhorde/cargo,tsurai/cargo,tshepang/cargo,tsurai/cargo,eminence/cargo,vojtechkral/cargo,nipunn1313/cargo,tsurai/cargo,tshepang/cargo,rust-lang/cargo,vojtechkral/cargo