Update launch_utils.py - fixes repetead package reinstalls

[illtellyoulater]

Description

Fixes failing dependency checks for extensions having a different package name and import name (for example ffmpeg-python / ffmpeg), which currently is causing the unneeded reinstall of packages at runtime.

In fact with the current code, the same string is used when installing a package and when checking for its presence, as you can see in the following example:

launch_utils.run_pip("install ffmpeg-python", "required package");

[ Installing required package: "ffmpeg-python" ... ] [ Installed ]

launch_utils.is_installed("ffmpeg-python");

False

...which would actually return true with:

launch_utils.is_installed("ffmpeg");

True

This PR modifies is_installed() from launch_utils.py so that it correctly confirms that a package is installed by returning a valid metadata object when passed the import name of an installed module, like this:

pkg_metadata = importlib.metadata.distribution(mod_name);

<importlib.metadata.PathDistribution object at 0x7fe14698a290>

I've been using this for a couple of months now, without noticing any issues at all (as documented by #13487)

In case the above method fails, the code tries validating for package existence using the previous method... which if IIRC was still useful in some specific conditions...

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests