v0.0-846-g7ef3690: [SymbolTable] Handle out-of-line task declarations.

Also add a metatype field to ReferenceComponent to verify that a reference
resolves to a symbol type that makes sense in its given context.

e.g.
  "function int class_cc::func_ff();"
  "class_cc" must resolve to a class definition.
  "func_ff" must resolve to a function declaration.

e.g.
  "mm #(.N(1)) mm_inst(.foo(...));"
  "N" must resolve to a parameter.
  "foo" must resolve to a data/net/var/instance.

Unit tests updated to verify metatype field.
Unit tests now cover metatype mismatches.

PiperOrigin-RevId: 350272612