matchers: add action name as opposed to full configuration

[kyessenov]

This is useful to reduce verbosity for string-value actions, e.g. picking a listener by name using the unified matchers.
Generally applicable to situations where many leaves are identical in a match tree.

Signed-off-by: Kuat Yessenov kuat@google.com

[kyessenov]

CC @snowp

[markdroth]

I assume this would work by passing in a map of name to action when invoking the matcher tree?

I'm okay with this in principle. @snowp, any concerns?

[kyessenov]

Yes, there is too much boilerplate when using string-valued actions (see the linked PR). Open to other ways but this looked least disruptive.