When a diagnostic belongs to a group that has a parent group (`GROUP_LINK` in `DiagnosticGroups.def`), display the full inheritance chain in the diagnostic output, including documentation hyperlinks and footnotes for each.
For example, a diagnostic in `ExistentialType` (child of `PerformanceHints`) now renders as:
```
warning: ... [#PerformanceHints::ExistentialType]
```
Groups without parents continue to display as before (`[#DeprecatedDeclaration]`).
Resolves rdar://170805800
This check will run on each type-checked primary input of the current compilation and emit a warning diagnostic for all discovered occurences of this code pattern when the performance hint diagnostic is enabled
Artem Chikin