Use updated linux runner path and fallback to legacy path

[cjsimon]

Addresses #62. Untested

Try to use the updated linux runner path introduced in flutter 3.27.0, else fallback to the original

I thought about refactoring using a private helper function, getContentLineByLine, but I wanted to preserve updating the filePath when using the legacyFilePath is successful

[cjsimon]

It seems that while there is a new CMakeLists.txt file in the new runner/ directory, the one in the top-level is still present, so the legacyLinuxCMakeListsPath path can be removed.

This might be slightly more complicated than I anticipated. I don't see a kFlutterWindowTitle in the new my_application.cc variant, but an APPLICATION_ID in the top-level CMakeLists.txt file, which I assume could serve as a new linux bundle id:

# The name of the executable created for the application. Change this to change
# the on-disk name of your application.
set(BINARY_NAME "Test")
# The unique GTK application identifier for this application. See:
# https://wiki.gnome.org/HowDoI/ChooseApplicationID
set(APPLICATION_ID "com.example.myapp")