Avoid ResourceWarnings during tests for /dev/null handle

[rmartin16]

After #867, pytest will raise for all Python errors including those normally suppressed. This change is also causing the errors/warnings below to be printed sometimes when pytest is run.

(venv3.10) rkm@eunectes briefcase % pytest tests/commands/new/test_call.py 
..
------------------------------------------------------------------------------
Ran 2 tests in 0.01s

OK
Exception ignored in: <_io.FileIO name='/dev/null' mode='wb' closefd=True>
ResourceWarning: unclosed file <_io.TextIOWrapper name='/dev/null' mode='w' encoding='utf-8'>

These changes ensure the file handle for /dev/null/ that's opened for the logfile Rich Console is closed before pytest` exits so this error is showed to developers and avoids subsequent confusion.

In practice, these errors are innocuous. Furthermore, end-users cannot see these errors unless they run a debug version of Python or use the -Werror (or perhaps the -Wdefault) flag.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[rmartin16]

Setting soft_wrap=True is no longer necessary since we always set it to True in console.py.

[codecov]

Codecov Report

Merging #879 (3c428fa) into main (9ab31c8) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
src/briefcase/console.py	100.00% <100.00%> (ø)
src/briefcase/commands/package.py	86.04% <0.00%> (ø)
src/briefcase/integrations/subprocess.py	100.00% <0.00%> (ø)
src/briefcase/commands/new.py	97.01% <0.00%> (+0.02%)	⬆️
src/briefcase/commands/publish.py	96.66% <0.00%> (+0.51%)	⬆️

[freakboy3742]

👍 Seems reasonable to me!