Rename parse_node -> node_id (#3760)

This was previously discussed at
https://discord.com/channels/655572317891461132/655578254970716160/1209975051588210729.
I'm initiating this mainly because we typically use "id" suffixes to
indicate an `IdBase` being passed around and the non-id suffix of
`parse_node` suggests at it carrying more data than it actually does.
There used to be more reason for avoiding `node_id` because
`SemIR::InstId` used to be named `NodeId`, but that's no longer
necessary. As a consequence, I'd like to rename `parse_node` to more
precisely reflect its type.

In full, this is doing:

```
parse_node_kind -> node_kind
parse_node -> node_id
ParseNodeCategory -> NodeCategory
ParseNodeKind -> NodeKind
ParseNode -> NodeId
```

This is primarily in check and sem_ir, but with some `parse_node_kind`
references in parse too.

Pluralization is consistent with name forms on both sides, so that
wasn't part of my replacements.

toolchain/check/impl.cpp

@@ -104,7 +104,7 @@ static auto BuildInterfaceWitness(
       }
     } else if (auto const_decl = decl.TryAs<SemIR::AssociatedConstantDecl>()) {
       // TODO: Check we have a value for this constant in the constraint.
-      context.TODO(context.insts().GetParseNode(impl.definition_id),
+      context.TODO(context.insts().GetNodeId(impl.definition_id),
                    "impl of interface with associated constant");
       return SemIR::InstId::BuiltinError;
     } else {
@@ -127,7 +127,7 @@ auto BuildImplWitness(Context& context, SemIR::ImplId impl_id)
   auto interface_type =
       context.types().TryGetAs<SemIR::InterfaceType>(impl.constraint_id);
   if (!interface_type) {
-    context.TODO(context.insts().GetParseNode(impl.definition_id),
+    context.TODO(context.insts().GetNodeId(impl.definition_id),
                  "impl as non-interface");
     return SemIR::InstId::BuiltinError;
   }