Rename parser dir to parse (#3178)

Continuing with #3070. Just a dir and file rename (mostly removing
prefixes, although for parse_tree_fuzzer and parse_tree_file_test I'm
dropping "tree" instead of "parse"). Everything in the parse dir should
be marked as a move.

toolchain/parse/handle_call_expression.cpp

@@ -0,0 +1,45 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "toolchain/parse/context.h"
+
+namespace Carbon::Parse {
+
+auto HandleCallExpression(Context& context) -> void {
+  auto state = context.PopState();
+
+  state.state = State::CallExpressionFinish;
+  context.PushState(state);
+
+  context.AddNode(NodeKind::CallExpressionStart, context.Consume(),
+                  state.subtree_start, state.has_error);
+  if (!context.PositionIs(Lex::TokenKind::CloseParen)) {
+    context.PushState(State::CallExpressionParameterFinish);
+    context.PushState(State::Expression);
+  }
+}
+
+auto HandleCallExpressionParameterFinish(Context& context) -> void {
+  auto state = context.PopState();
+
+  if (state.has_error) {
+    context.ReturnErrorOnState();
+  }
+
+  if (context.ConsumeListToken(NodeKind::CallExpressionComma,
+                               Lex::TokenKind::CloseParen, state.has_error) ==
+      Context::ListTokenKind::Comma) {
+    context.PushState(State::CallExpressionParameterFinish);
+    context.PushState(State::Expression);
+  }
+}
+
+auto HandleCallExpressionFinish(Context& context) -> void {
+  auto state = context.PopState();
+
+  context.AddNode(NodeKind::CallExpression, context.Consume(),
+                  state.subtree_start, state.has_error);
+}
+
+}  // namespace Carbon::Parse