Merge #2641

2641: Parse const generics r=matklad a=roblabla

Adds very primitive support for parsing const generics (`const IDENT: TY`) so that rust-analyzer stops complaining about the syntax being invalid.

Fixes #1574
Fixes #2281 

Co-authored-by: roblabla <unfiltered@roblab.la>

crates/ra_parser/src/syntax_kind/generated.rs

@@ -229,6 +229,7 @@ pub enum SyntaxKind {
     TYPE_PARAM_LIST,
     LIFETIME_PARAM,
     TYPE_PARAM,
+    CONST_PARAM,
     TYPE_ARG_LIST,
     LIFETIME_ARG,
     TYPE_ARG,