Named arguments in commands + many grammar fixes (#20994)

* Breaking parser changes, implement https://github.com/nim-lang/RFCs/issues/442

Types are separated from expressions and better reflected in the grammar.

* add test

* more accurate grammar

* fix keyword typedescs

* accept expressions in proc argument lists

* CI "fixes"

* fixes

* allow full ref expressions again, adapt old tests

* cleanup, fix some tests

* improve grammar, try and revert semtypes change

* restrict sigil binding to identOrLiteral

* fix, should have caught this immediately

* add changelog entry, fix double not nil bug

* correct grammar

* change section

* fix

* real fix hopefully

* fix test

* support LL(1) for tuples

* make grammar.txt too

tests/parser/ttypeexprs.nim

@@ -0,0 +1,25 @@
+proc foo[T: ptr int | ptr string](x: T) = discard
+var x = "abc"
+foo(addr x)
+
+let n = 3'u32
+type Double = (
+  when n.sizeof == 4: uint64
+  elif n.sizeof == 2: uint32
+  else: uint16
+)
+
+type
+  A = (ref | ptr | pointer)
+  B = pointer | ptr | ref
+  C = ref | ptr | pointer
+
+template `+`(a, b): untyped = (b, a)
+template `*`(a, b): untyped = (a, b)
+
+doAssert (ref int + ref float * ref string + ref bool) is
+  (ref bool, ((ref float, ref string), ref int))
+type X = ref int + ref float * ref string + ref bool
+doAssert X is (ref bool, ((ref float, ref string), ref int))
+
+type SomePointer = proc | ref | ptr | pointer