chore: move cli/tests/ -> tests/ (#22369)

This looks like a massive PR, but it's only a move from cli/tests ->
tests, and updates of relative paths for files.

This is the first step towards aggregate all of the integration test
files under tests/, which will lead to a set of integration tests that
can run without the CLI binary being built.

While we could leave these tests under `cli`, it would require us to
keep a more complex directory structure for the various test runners. In
addition, we have a lot of complexity to ignore various test files in
the `cli` project itself (cargo publish exclusion rules, autotests =
false, etc).

And finally, the `tests/` folder will eventually house the `test_ffi`,
`test_napi` and other testing code, reducing the size of the root repo
directory.

For easier review, the extremely large and noisy "move" is in the first
commit (with no changes -- just a move), while the remainder of the
changes to actual files is in the second commit.

tests/unit_node/testdata/process_really_exit.ts

@@ -0,0 +1,10 @@
+import process from "node:process";
+
+//deno-lint-ignore no-undef
+// @ts-ignore - Node typings don't even have this because it's
+// been deprecated for 4 years. But it's used in `signal-exit`,
+// which in turn is used in `node-tap`.
+process.reallyExit = function () {
+  console.info("really exited");
+};
+process.exit();