[qt, settings] allow to set custom unit and battery serial (#2813)

Also removes "use dev keys" option since it's not even present on UI and it's just a file redirection anyways
Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/2813
Reviewed-by: Caio Oliveira <caiooliveirafarias0@gmail.com>
Reviewed-by: crueter <crueter@eden-emu.dev>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

docs/user/Native.md

@@ -0,0 +1,12 @@
+# User Handbook - Native Application Development
+
+Debugging on physical hardware can get tedious and time consuming. Users are empowered with the debugging capabilities of the emulator to ensure their applications run as-is on the system. To the greatest extent possible atleast.
+
+## Debugging
+
+**Standard key prefix**: Allows to redirect the key manager to a file other than `prod.keys` (for example `other` would redirect to `other.keys`). This is useful for testing multiple keysets. Default is `prod`.
+
+**Changing serial**: Very basic way to set debug values for the serial (and battery number). Developers do not need to write the full serial as it will be writen in-place (that is, it will be filled with the default serial and then overwrite the serial from the beginning).
+- Battery serial: `YUZU0EMULATOR14022024`
+- Board serial: `YUZ10000000001`
+If the user were to set their board serial as `ABC`, then it will be written in-place and the resulting serial would be `ABC10000000001`. There are no underlying checks to ensure correctness of serials other than a hard limit of 16-characters for both.

docs/user/README.md

@@ -11,3 +11,4 @@ This handbook is primarily aimed at the end-user - baking useful knowledge for e
 - **[Testing](Testing.md)**
 - **[Data, savefiles and storage](Storage.md)**
 - **[Orphaned Profiles](Orphaned.md)**
+- **[Native Application Development](Native.md)**