Reduce size of TypeScript Compiler snapshot (#6809)

This PR is intentionally ugly. It duplicates all of the code in cli/js2/ into
cli/tsc/  ... because it's very important that we all understand that this code
is unnecessarily duplicated in our binary. I hope this ugliness provides the
motivation to clean it up.

The typescript git submodule is removed, because it's a very large repo and
contains all sorts of stuff we don't need. Instead the necessary files are
copied directly into the deno repo. Hence +200k lines.

COMPILER_SNAPSHOT.bin size
```
master         3448139
this branch    3320972
```

Fixes #6812

1 files changed, 23 insertions, 0 deletions

diff --git a/cli/tsc/01_internals.js b/cli/tsc/01_internals.js
new file mode 100644
index 000000000..eee9eeaf7
--- /dev/null
+++ b/cli/tsc/01_internals.js
@@ -0,0 +1,23 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+((window) => {
+  const internalSymbol = Symbol("Deno.internal");
+
+  // The object where all the internal fields for testing will be living.
+  const internalObject = {};
+
+  // Register a field to internalObject for test access,
+  // through Deno[Deno.internal][name].
+  function exposeForTest(name, value) {
+    Object.defineProperty(internalObject, name, {
+      value,
+      enumerable: false,
+    });
+  }
+
+  window.__bootstrap.internals = {
+    internalSymbol,
+    internalObject,
+    exposeForTest,
+  };
+})(this);