Miscellaneous UI updates

[cgutman]

Description

This PR contains a grab bag of mostly unrelated UI changes and adds the option for using non-lowpower HEVC encoding on Intel (see #2175)

Changes:

• Add option to use non-lowpower HEVC encoding on Intel
• Move UPnP option to the top of the Network tab, since it's by far the most commonly used option there
• Fixes the automatic gamepad type selection option appearing on Linux and Mac where it is not supported
• Adjusted the wording of the NVENC latency over power option to be more clear
• Renamed and moved the Channels option from the Advanced tab to the General tab and renamed it to something more descriptive
• Added a note to help users remember to enclose command paths in quotes if they contain spaces
• Renamed and moved the Files tab to feature less prominently in the UI since it's almost never used
• Added a friendlier message when the encoder wasn't found

Screenshot

Issues Fixed or Closed

Fixes #2175

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

LizardByte requires that branches be up-to-date before merging. This means that after any PR is merged, this branch
must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[ReenigneArcher]

Since some of the options were re-ordered, can you re-order them here as well?

[cgutman]

I moved UPnP, Channels, and the Config Files section. I think that's everything.

[ReenigneArcher]

Maybe we should add a note to indicate that the multiple clients will stream and control the same session. There seems to be some confusion about that.

[cgutman]

OK, I added a note to that effect in the docs and the UI.

[ReenigneArcher]

Just a question... do we accept any standard shell/terminal command including things such as piping, &&, ||, >, etc.

I wonder if we should add an option to select the shell to use and then just pass in their command as an argument to that shell. (Not for this PR, just an idea I've had for a little while)

[cgutman]

We don't currently, since those are shell builtins rather than real executables. I had similar thoughts when I was working on that URL support for Windows (and we do shell out to cmd.exe in some cases there too).

One problem is that we've already exposed shell-like features like output redirection in the UI as a separate option. It might be difficult to make that work properly with a true shell invocation since the command itself could be piping stdout somewhere else.

[ReenigneArcher]

Rebasing should fix the flatpak build