Windows: text input

[clarkezone]

Bring the Linux embedder keyboard input support over to the Windows embedder.

[stuartmorgan-g]

Pushed changes that fix Linux. It ended up being kind of ugly since making my GN include/ aggregation not flatten the structure was non-trivial, so there are a few conditional includes in the Linux code now. Once build systems is settled I can improve the situation.

Some things to note:

• I moved the files some more; common/include/ is now just include/, and common/src/ is now just common/, since having include/ be right under library/ makes more sense in the Make-style build where clients are pointing a tree locations for includes. I edited the VS projects manually on Linux to account for that, but I expect I missed something and you'll need to clean that up.
• I merged with master to resolve conflicts with the changes from adding key events on Linux. Feel free to leave key events for Windows out of this patch, but it might be worth adding that file and seeing if it Just Works given that it's all GLFW.

[stuartmorgan-g]

Feel free to leave key events for Windows out of this patch, but it might be worth adding that file and seeing if it Just Works given that it's all GLFW.

I decided to test this branch out on Windows to see if I broke anything, and then thought I'd check this. It does work, as expected: https://github.com/stuartmorgan/flutter-desktop-embedding/tree/windows-key-events

I'll land that as a follow-up patch to avoid adding even more things to this patch though.

[clarkezone]

Feel free to leave key events for Windows out of this patch, but it might be worth adding that file and seeing if it Just Works given that it's all GLFW. ...

@stuartmorgan will do

_{Sent with GitHawk}

[clarkezone]

All done, awaiting input.

[stuartmorgan-g]

Looking good! Just a few minor things (I'd fix them myself, but I don't have my Windows machine at the moment and don't want to accidentally break something with an untested change).

[stuartmorgan-g]

Oh, and if you want to do the honors you could remove the final caveat from the main README in this patch :)

[clarkezone]

OK, all done here!

[stuartmorgan-g]

🎉