linux-pipewire: Fix memory leaks

[dimtpap]

Description

Fixes memory leaks in the linux-pipewire plugin.

1. pw_node_infos copied here were never freed
2. pw_registry proxy created here was never freed

Motivation and Context

Memory leaks are bad.

How Has This Been Tested?

Tried camera capture, unplugged and plugged in a camera several times, tried screen capturing, destroyed the sources. Everything works. LeakSanitizer does not report the leaks anymore.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.