Update Linux related Flutter initialization files

[SleepySquash]

Synopsis

Linux doesn't run as of now.

Solution

This PR recreates CPP and CMake files for Linux configuration, which fixes the issue.

Checklist

• Created PR:
  • [x] In draft mode
  • [x] Name contains issue reference
  • [x] Has type and k:: labels applied
• Before review:
  • [x] Documentation is updated (if required)
  • [x] Tests are updated (if required)
  • [x] Changes conform code style
  • [x] CHANGELOG entry is added (if required)
  • [x] FCM (final commit message) is posted or updated
  • [x] Draft mode is removed
• [x] Review is completed and changes are approved
  • [x] FCM (final commit message) is approved
• Before merge:
  • [x] Milestone is set
  • [x] PR's name and description are correct and up-to-date
  • [x] All temporary labels are removed

[SleepySquash]

FCM

Update `CMakeLists.txt` and `my_application.cc` files for Linux (#1128)