Avoid copying of immutables from cache and None on retry

[frost-nzcr4]

Pull Request check-list

Please make sure to review and check all of these items:

• Do tests and lints pass with this change?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?
• Was the change added to CHANGES file?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Description of change

• The first commit is to stop copying the None value, which improves performance by 13x (it also needs to be cherry-picked to 5.0 branch):

  from timeit import timeit
  timeit("deepcopy(retry)", "from copy import deepcopy; retry = None")
  # 0.11874631093814969
  timeit("retry if retry is None else deepcopy(retry)", "from copy import deepcopy; retry = None")
  # 0.009135799948126078

• The second commit is to stop copying immutable objects, which improves performance by 2x for None and by 6x at least for bytes and strings:

  timeit(
  """deepcopy(cache["get"]["response"])""",
  """
  from collections import OrderedDict
  from copy import deepcopy
  
  cache = OrderedDict()
  cache["get"] = {"response": None}
  """
  )
  # 0.14101774094160646
  
  timeit(
  """cache["get"]["response"] if isinstance(cache["get"]["response"], IMMUTABLES) else deepcopy(cache["get"]["response"])""",
  """
  from collections import OrderedDict
  from copy import deepcopy
  
  IMMUTABLES = (bytes, str, int, float, bool, type(None), tuple)
  cache = OrderedDict()
  cache["get"] = {"response": None}
  """
  )
  # 0.079819873906672
  
  timeit(
  """response if isinstance(response, IMMUTABLES) else deepcopy(response)""",
  """
  from collections import OrderedDict
  from copy import deepcopy
  
  IMMUTABLES = (bytes, str, int, float, bool, type(None), tuple)
  cache = OrderedDict()
  cache["get"] = {"response": None}
  response = cache["get"]["response"]
  """
  )
  # 0.05251034500543028

[frost-nzcr4]

Fixed the linter error.