Simplify build-system further

Remove Fragile from the list of dependencies

It is not necessary for building 'gio' anymore,
since the upgrade to 'glib v2_58'.

Remove "online" and "reset_lock" Meson-options

Building Squeekboard should work offline.

Use a single "Cargo.toml"-file instead of splitting it into parts

and putting it back together when building.

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/623>

tools/meson.build

@@ -16,5 +16,4 @@ test_layout = custom_target('squeekboard-test-layout',
         + cargo_build_flags,
     install: true,
     install_dir: bindir,
-    depends: cargo_deps,
 )