automatic map spreading on interop calls with named parameters

When a method, function or constructor expects named parameters but that it receives an odd number of arguments (positional ones not counted) then the last argument is considered to evaluate to a map and is replaced by all missing parameters being passed valued looked up in the map.

It must be taken care of:

• evaluating the map argument only once
• re-emitting default values; problem is that some default values depend on private lib elements and so can't be injected in user-code, we should warn in such cases and treat them as required (unless nullable which is unlikely)
• throwing an error at compile time if the call site is dynamic.

No files, tests, or entry points are named; begin by locating the compiler code that handles Clojure-to-Dart interop calls and named parameters. The work is complete when map spreading handles evaluation and defaults as described, warns for inaccessible private defaults, and rejects dynamic call sites at compile time.