feat: implemented unicode input mode

[ABeltramo]

Description

This PR adds Unicode support for remote pasting in Linux using Unicode input mode.

I've read around and this might not be supported on all combinations of DE, for example see: kde#103788 it works fine on my machine but maybe some Linux wizard can find a better solution.

I've introduced another Boost dependency: Boost.locale I've added it as a dependency where I could find it, but feel free to modify the PR if I've missed some.

Issues Fixed or Closed

Fixes #760

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

[CLAassistant]

All committers have signed the CLA.

[ReenigneArcher]

Some simple build errors:

• add boost locale
  • (flatpak) https://github.com/ABeltramo/Sunshine/blob/954968ce24119332853fe4dc820d2c5126a76f6d/packaging/linux/flatpak/dev.lizardbyte.sunshine.yml#L36
  • (appimage) https://github.com/ABeltramo/Sunshine/blob/954968ce24119332853fe4dc820d2c5126a76f6d/.github/workflows/CI.yml#L284
  • (docs) https://github.com/ABeltramo/Sunshine/blob/linux-utf8/docs/source/building/linux.rst#ubuntu-2004
  • (docs) https://github.com/ABeltramo/Sunshine/blob/linux-utf8/docs/source/building/linux.rst#ubuntu-2204

[t184256]

ibus and fcitx5 only support (Ctrl-Shift-U then digits then Return). I can't find an input method that'd support Ctrl-Shift-(U-then-digits)