gh-90699: Use module state to access insert str object.

[corona10]

importpyperfrunner=pyperf.Runner()
runner.timeit(name="bench bisect",
stmt="""bisect.insort(a, 30)""",
setup="""import bisectclass A(list): passa = A(range(1000))"""
)

Mean +- std dev: [main] 1.14 us +- 0.01 us -> [module] 1.06 us +- 0.01 us: 1.07x faster

[corona10]

Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 5.14 Run tests sequentially
0:00:00 load avg: 5.14 [1/1] test_bisect
beginning 6 repetitions
123456
......
== Tests result: SUCCESS ==
1 test OK.
Total duration: 210 ms
Tests result: SUCCESS