Some TYPEDDATA objects allocate struct fields using the GC right after
they get created, and in that case the VM can try to perform a GC and join
a barrier if another ractor started one. If we're dumping the heap in another
ractor, this acquires a barrier and it will call the `rb_obj_memsize` function on this
object. We can't assume these struct fields are non-null. This also goes for C extensions,
which may cause problems with heap dumping from a ractor if their memsize functions aren't
coded correctly to check for NULL fields. Because dumping the heap from a ractor is likely a
rare scenario and it has only recently been introduced, we'll have to see how this works in
practice and if it causes bugs.

Add locations to struct `RNode_SCLASS`.

memo:

```
@ ProgramNode (location: (1,0)-(1,18))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,18))
    +-- body: (length: 1)
        +-- @ SingletonClassNode (location: (1,0)-(1,18))
            +-- locals: []
            +-- class_keyword_loc: (1,0)-(1,5) = "class"
            +-- operator_loc: (1,6)-(1,8) = "<<"
            +-- expression:
            |   @ SelfNode (location: (1,9)-(1,13))
            +-- body: nil
            +-- end_keyword_loc: (1,15)-(1,18) = "end"
```

Add locations to struct `RNode_IN`.

memo:

```bash
> ruby -e 'case 1; in 2 then 3; end' --parser=prism --dump=parsetree
@ ProgramNode (location: (1,0)-(1,24))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,24))
    +-- body: (length: 1)
        +-- @ CaseMatchNode (location: (1,0)-(1,24))
            +-- predicate:
            |   @ IntegerNode (location: (1,5)-(1,6))
            |   +-- IntegerBaseFlags: decimal
            |   +-- value: 1
            +-- conditions: (length: 1)
            |   +-- @ InNode (location: (1,8)-(1,19))
            |       +-- pattern:
            |       |   @ IntegerNode (location: (1,11)-(1,12))
            |       |   +-- IntegerBaseFlags: decimal
            |       |   +-- value: 2
            |       +-- statements:
            |       |   @ StatementsNode (location: (1,18)-(1,19))
            |       |   +-- body: (length: 1)
            |       |       +-- @ IntegerNode (location: (1,18)-(1,19))
            |       |           +-- IntegerBaseFlags: decimal
            |       |           +-- value: 3
            |       +-- in_loc: (1,8)-(1,10) = "in"
            |       +-- then_loc: (1,13)-(1,17) = "then"
            +-- else_clause: nil
            +-- case_keyword_loc: (1,0)-(1,4) = "case"
            +-- end_keyword_loc: (1,21)-(1,24) = "end"
```

Add `keyword_module` amd `keyword_end` locations to struct `RNode_MODULE`.

memo:
```
>ruby --dump=parsetree -e 'module A end'
@ ProgramNode (location: (1,0)-(1,12))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,12))
    +-- body: (length: 1)
        +-- @ ModuleNode (location: (1,0)-(1,12))
            +-- locals: []
            +-- module_keyword_loc: (1,0)-(1,6) = "module"
            +-- constant_path:
            |   @ ConstantReadNode (location: (1,7)-(1,8))
            |   +-- name: :A
            +-- body: nil
            +-- end_keyword_loc: (1,9)-(1,12) = "end"
            +-- name: :A
```

Add keyword_defined locations to struct RNode_DEFINED

The following Location information has been added This is the information required for parse.y to be a universal parser:

```
❯ ruby --parser=prism --dump=parsetree -e "class A < B; end"
@ ProgramNode (location: (1,0)-(1,16))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,16))
    +-- body: (length: 1)
        +-- @ ClassNode (location: (1,0)-(1,16))
            +-- locals: []
            +-- class_keyword_loc: (1,0)-(1,5) = "class"
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- constant_path:
            |   @ ConstantReadNode (location: (1,6)-(1,7))
            |   +-- name: :A
            +-- inheritance_operator_loc: (1,8)-(1,9) = "<"
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- superclass:
            |   @ ConstantReadNode (location: (1,10)-(1,11))
            |   +-- name: :B
            +-- body: nil
            +-- end_keyword_loc: (1,13)-(1,16) = "end"
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- name: :A
```

The following Location information has been added This is the information required for parse.y to be a universal parser:

```
❯ ruby --parser=prism --dump=parsetree -e "END {  }"
@ ProgramNode (location: (1,0)-(1,8))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,8))
    +-- body: (length: 1)
        +-- @ PostExecutionNode (location: (1,0)-(1,8))
            +-- statements: nil
            +-- keyword_loc: (1,0)-(1,3) = "END"
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- opening_loc: (1,4)-(1,5) = "{"
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- closing_loc: (1,7)-(1,8) = "}"
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```