Igniter: Allow custom Qt scale factor rounding policy

[iLLiCiTiT]

Changelog Description

Do not force PassThrough rounding policy if different policy is defined via env variable.

Additional info

On some virtual machines is PassThrough rounding policy causing issues with calculated widget rectangle and paint rectangle. Painted rectangle has expected rectangle, but handling of events happens in smaller and offset rectangle. Probably caused by some bug in Qt. Widgets on top left are closer to expected behavior, bottom right is worse.

Testing notes:

You must have some scaling set (e.g. 125% on windows).

1. Set environment variable QT_SCALE_FACTOR_ROUNDING_POLICY to e.g. "Floor"
2. Launch OpenPype so igniter is shown
3. The size of igniter should be rounded by the policy you set to env variable

[64qam]

When set a mongo string and OP is starting:

--- launching setup UI ...
Traceback (most recent call last):
  File "C:\Users\qam\code\OpenPype\igniter\install_thread.py", line 166, in run
    local_openpype = bs.create_version_from_live_code()
  File "C:\Users\qam\code\OpenPype\igniter\bootstrap_repos.py", line 697, in create_version_from_live_code
    self._create_openpype_zip(temp_zip, repo_dir)
  File "C:\Users\qam\code\OpenPype\igniter\bootstrap_repos.py", line 867, in _create_openpype_zip
    sha256sum(sanitize_long_path(file.as_posix())),
  File "C:\Users\qam\code\OpenPype\igniter\bootstrap_repos.py", line 74, in sha256sum
    with open(filename, 'rb', buffering=0) as f:
FileNotFoundError: [Errno 2] No such file or directory: '\\\\?\\C:\\Users\\qam\\code\\OpenPype\\schema'```

[BigRoy]

@64qam that sounds like a bug that might come from this PR: #5265 but shouldn't originate from the current PR you commented on.

[iLLiCiTiT]

When set a mongo string and OP is starting:

Unrelated to this PR. Fixed in #5557