Allow for ChildContent Context parameter name to be specified on the parent component declaration

Hey, i ran into this issue
dotnet/roslyn#85422 (Resolve ambiguous parameter name context using the closest one)
because of nested components each having exactly one ChildContent and overlapping Context names ("context").

I would like to suggest allowing for specifying the name of the ChildContent's Context name in the declaration of the parent component, thus fullfilling the role of ChildContent, which is saving lines and nesting.

So instead of having to do this:
```xml

```
I would allow for this:
```xml

```

Start by reading the ambiguity behavior referenced in dotnet/roslyn#85422 and compare it with the two nested-component examples in this issue. Trace where parent component declarations and ChildContent Context names are parsed or resolved. Done means the proposed declaration syntax is specified, implemented, and the nested example resolves the requested context name without the explicit ChildContent block.

Written by the indexing model from the issue text.