gh-121973: Fix flaky test_pyrepl tests (GH-122140)

This fixes the flakiness in:
* test_inspect_keeps_globals_from_inspected_file
* test_inspect_keeps_globals_from_inspected_module

The output already includes newlines. Adding newlines for every entry in
the output list introduces non-determinism because it added '\n' in
places where stdout is flushed or some buffer becomes full.

The regex also needed to be updated because pyrepl includes control
characters -- the visible output on each line doesn't immediately follow
a newline character.

Co-authored-by: Łukasz Langa <lukasz@langa.pl>

Lib/test/test_pyrepl/test_pyrepl.py

@@ -963,7 +963,7 @@ def _run_repl_globals_test(self, expectations, *, as_file=False, as_module=False
  mod = blue / "calx.py"
  mod.write_text("FOO = 42", encoding="utf-8")
  commands = [
- "print(f'{" + var + "=}')" for var in expectations
+ "print(f'^{" + var + "=}')" for var in expectations
  ] + ["exit()"]
  if as_file and as_module:
  self.fail("as_file and as_module are mutually exclusive")
@@ -989,10 +989,10 @@ def _run_repl_globals_test(self, expectations, *, as_file=False, as_module=False
  self.assertEqual(exit_code, 0)
  for var, expected in expectations.items():
  with self.subTest(var=var, expected=expected):
- if m := re.search(rf"[\r\n]{var}=(.+?)[\r\n]", output):
+ if m := re.search(rf"\^{var}=(.+?)[\r\n]", output):
  self._assertMatchOK(var, expected, actual=m.group(1))
  else:
- self.fail(f"{var}= not found in output")
+ self.fail(f"{var}= not found in output: {output!r}\n\n{output}")
 
  self.assertNotIn("Exception", output)
  self.assertNotIn("Traceback", output)
@@ -1126,4 +1126,4 @@ def run_repl(
  except subprocess.TimeoutExpired:
  process.kill()
  exit_code = process.wait()
- return "\n".join(output), exit_code
+ return "".join(output), exit_code