Fix various resolved types of const pointers

[FnControlOption]

Alternative to #2265

• Added a Binding struct that has two fields: type: Type and is_const: bool. Examples of when is_const is true are:
  1. An identifier that refers to a primitive, such as i32 and true
  2. An identifier foo that refers to a previously declared const foo
  3. An expression of the form &foo (i.e. &&foo is of type *const *Foo for a given var foo: Foo)
  4. A char/number/enum/string literal (i.e. &'a' is a *const comptime_int, &42 is a *const comptime_int, &.foo is a *const @Type(.enum_literal), &"foo" is a *const *const [3:0]u8)
• Added three new functions: resolveBindingOfNode{,Internal,Uncached}
  • resolveTypeOfNode{,Internal} are now just helper functions that delegate to resolveBindingOfNode{,Internal}
  • resolveTypeOfNodeUncached still handles most AST nodes except for the following which are now handled by resolveBindingOfNodeUncached:
    • identifier
    • address_of
    • field_access
    • slice
    • slice_sentinel
    • slice_open
    • array_access
  • The current design allows most type resolution to happen in resolveTypeOfNodeUncached, while more special cases involving mutability can be handled in resolveBindingOfNodeUncached.

[FnControlOption]

Updated PR description