Install icons to hicolor theme on Linux

[kodemeister]

Description

For now Sunshine installs icons directly to /usr/share/icons. This is generally discouraged. According to freedesktop spec, well-behaved applications should put their icons under /usr/share/icons/hicolor directory instead of /usr/share/icons. This PR changes the installation paths as following:

• Application icon goes into /usr/share/icons/hicolor/scalable/apps
• Tray icons go into /usr/share/icons/hicolor/scalable/status

Note that I also made a copy of sunshine.svg and renamed it to sunshine-tray.svg. This allows us to have two separate icons: sunshine.svg for DE main menu and sunshine-tray.svg for tray. So even in case when Sunshine is compiled without tray support, sunshine.svg will be still installed and displayed in the main menu. In future we might also want distinct Sunshine icons, e.g. larger colorful icon for the main menu and smaller monochrome icon for tray.

Screenshot

Issues Fixed or Closed

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]

Thank you for the PR. This mostly looks okay, but I don't think I agree with duplicating the sunshine.svg to sunshine-tray.svg... "DRR"

Could still install the the sunshine.svg to two locations though...

[kodemeister]

No problem, I've removed the copy of sunshine.svg. Now the same sunshine.svg is installed to two locations:

1. /usr/share/icons/hicolor/scalable/apps/sunshine.svg
2. /usr/share/icons/hicolor/scalable/status/sunshine-tray.svg