Support Python 3.14.0rc2, test on CI - #14967

FAILED tests/test_text.py::test_eval_formatter -   File "<string>", line 1
    0[n//i for i in range(1,8)]
           ^^^
SyntaxError: invalid syntax

FAILED tests/test_completer.py::TestCompleter::test_all_completions_dups - AssertionError: (True, [])
assert [] == ['TestClass']
  
  Right contains one more item: 'TestClass'
  
  Full diff:
  + []
  - [
  -     'TestClass',
  - ]
FAILED tests/test_completer.py::TestCompleter::test_completion_have_signature - StopIteration
FAILED tests/test_completer.py::TestCompleter::test_deduplicate_completions - AssertionError: Completions (Z.z<tab>) correctly deduplicate: [] 
assert 0 == 1
 +  where 0 = len([])
FAILED tests/test_completer.py::TestCompleter::test_greedy_completions - AssertionError: <Completion start=5 end=5 text='real' type='?', signature='?',> not found in []
FAILED tests/test_completer.py::TestCompleter::test_jedi - AssertionError: jedi >0.9 should complete and not crash
assert <Completion start=6 end=6 text='real' type='?', signature='?',> in set()
 +  where <Completion start=6 end=6 text='real' type='?', signature='?',> = Completion(6, 6, 'real')
FAILED tests/test_completer.py::TestCompleter::test_matcher_suppression_with_jedi - AssertionError: 'keys' not found in []
FAILED tests/test_debugger.py::tests.test_debugger.can_exit
FAILED tests/test_debugger.py::tests.test_debugger.can_quit
FAILED tests/test_debugger.py::tests.test_debugger.test_ipdb_magics2
FAILED tests/test_debugger.py::test_decorator_skip_with_breakpoint - pexpect.exceptions.TIMEOUT: Timeout exceeded.
FAILED tests/test_text.py::test_eval_formatter -   File "<string>", line 1
    0[n//i for i in range(1,8)]
           ^^^
SyntaxError: invalid syntax

FAILED tests/test_debugger.py::tests.test_debugger.can_exit
FAILED tests/test_debugger.py::tests.test_debugger.can_quit
FAILED tests/test_debugger.py::tests.test_debugger.test_ipdb_magics2
FAILED tests/test_debugger.py::test_decorator_skip_with_breakpoint - pexpect.exceptions.TIMEOUT: Timeout exceeded.
FAILED tests/test_text.py::test_eval_formatter -   File "<string>", line 1
    0[n//i for i in range(1,8)]
           ^^^
SyntaxError: invalid syntax
=================== 5 failed, 1415 passed, 136 skipped, 3 xfailed, 42 warnings in 134.82s (0:02:14) ====================