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/node_stack.cpp

@@ -21,13 +21,12 @@ auto NodeStack::PrintForStackDump(llvm::raw_ostream& output) const -> void {
 
   output << "NodeStack:\n";
   for (auto [i, entry] : llvm::enumerate(stack_)) {
-    auto parse_node_kind = parse_tree_->node_kind(entry.parse_node);
-    output << "\t" << i << ".\t" << parse_node_kind;
-    switch (parse_node_kind) {
-#define CARBON_PARSE_NODE_KIND(Kind)                                   \
-  case Parse::NodeKind::Kind:                                          \
-    print_id.operator()<ParseNodeKindToIdKind(Parse::NodeKind::Kind)>( \
-        entry.id);                                                     \
+    auto node_kind = parse_tree_->node_kind(entry.node_id);
+    output << "\t" << i << ".\t" << node_kind;
+    switch (node_kind) {
+#define CARBON_PARSE_NODE_KIND(Kind)                                        \
+  case Parse::NodeKind::Kind:                                               \
+    print_id.operator()<NodeKindToIdKind(Parse::NodeKind::Kind)>(entry.id); \
     break;
 #include "toolchain/parse/node_kind.def"
     }