Missing CONTAINS_SPLAT counterpart for Hash nodes

[amomchilov]

Arrays have the PM_ARRAY_NODE_FLAGS_CONTAINS_SPLAT flag, which tells you if there's a *splat, or if all the elements are just plain elements.

prism/config.yml

Lines 661 to 664 in acfeade

	- name: ArrayNodeFlags
	values:
	- name: CONTAINS_SPLAT
	comment: "if array contains splat nodes"

There's nothing equivalent to this for PM_HASH_NODE or PM_KEYWORD_HASH_NODE for knowing whether or not there's a **splat, so each element needs to always be type-checked for PM_ASSOC_NODE vs PM_ASSOC_SPLAT_NODE.

[kddnewton]

@amomchilov is this something you would need for Sorbet? I'm trying to figure out the use-case here. The flags in the array are because you might be able to get away with not duplicating an array if there's a splat, so it's mostly a compiler-level concern.