Improve template tokenizing (#13919)

* add benchmarks

* refactor: tokenize template as middle + tail

* perf: avoid push tc.brace

* refactor: overwrite skipSpace in jsx plugin

* transform tl.templateMiddle/Tail

* refactor: simplify JSX context tracking

* fix flow error

* refactor: move JSX context to context.js

* fix: ensure comment stack is correctly handled

* rename createPositionFromPosition

* rename token type and methods

* add tokenIsTemplate

* refactor: merge babel 7 logic in babel7CompatTokens

* fix flow error

benchmark/babel-parser/many-nested-block-elements/bench.mjs

@@ -0,0 +1,22 @@
+import Benchmark from "benchmark";
+import baseline from "@babel-baseline/parser";
+import current from "@babel/parser";
+import { report } from "../../util.mjs";
+
+const suite = new Benchmark.Suite();
+function createInput(length) {
+  return "{".repeat(length) + "0" + "}".repeat(length);
+}
+function benchCases(name, implementation, options) {
+  for (const length of [128, 256, 512, 1024]) {
+    const input = createInput(length);
+    suite.add(`${name} ${length} nested template elements`, () => {
+      implementation.parse(input, options);
+    });
+  }
+}
+
+benchCases("baseline", baseline);
+benchCases("current", current);
+
+suite.on("cycle", report).run();