Remove external dependency on grep from netmiko-show

[ReK42]

This PR allows netmiko-show to run cross-platform via pure Python. Tested on Windows 11 in Python 3.11 and 3.7.

Also added --write-output, which will dump the output to files in the PWD rather than printing to stdout.

Minor, non-impacting edits to other files courtesy of running black and ruff, and adding a couple things to .gitignore. All substantial edits are in netmiko/cli_tools/netmiko-show.py.

[ktbyers]

@ReK42 Were you using the version of black specified in Netmiko's pyproject.toml. You should use exactly that version of black (otherwise the project will have too much unnecessary changes just do to minor black version changes)?

We should get rid of all of these linting changes.

I try to roll black version only at releases to minimize some of the impact of these unneeded linting changes.

[ReK42]

Reverted that commit. I had used the latest version of black from pypi.