This commit extends the template targeting system, which determines the node
being referenced given a template position, to return additional context if
needed about the particular aspect of the node to which the position refers.
For example, a position pointing to an element node may be pointing either
to its tag name or to somewhere in the node body. This is the difference
between `<div|>` and `<div foo | bar>`.
PR Close#40032
Alex Rickabaugh
ccaf48de8f