Expand usage of title trait

[hpmellema]

Closes: #2406

Description

Expands the selector of the title trait to allow it to be applied to any non-member shape.

The title trait provides a simple name or description that can be used when referencing the shape from another context.

In a code generator this can be used to provide helpful documentation For example you could use the title trait on the following error:

@title("Indicates a failed doodad.") 
@error("client")
structure OopsieDaisyError {...}

Which could then referenced in a generated operation (notional java):

/**
  * My Cool operation that does stuff.
  * 
  * @throws OopsieDaisyError - Indicates a failed doodad.
  */
  public MyOuput myOperation(MyInput input) {...}

Notice how the title trait provides the user-friendly description to use in the operation context

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