android: add missing support for key modifiers - #403

The translation table only covered letters, digits, arrows,
Enter, Tab, Space, Backspace, Shift / Alt, comma + period —
which means a hardware keyboard on Android (tablet + Bluetooth /
USB / Magic Keyboard; ChromeOS; Stage Manager iPad with a Mac
keyboard) couldn't reach the host app with most of its keys.

Adds the keys that have a clear semantic and a matching `KeyCode`
variant:

- Modifiers: Ctrl L/R, Meta L/R (Cmd on Apple keyboards), CapsLock,
  NumLock, ScrollLock. PR #403 already wired the `KeyMods` tracking
  for Ctrl / Super, but that's a no-op as long as the keycodes
  themselves translate to `KeyCode::Unknown`.
- Edit cluster: Escape, Insert, Delete (`KEYCODE_FORWARD_DEL`,
  distinct from the existing `KEYCODE_DEL` → Backspace), MoveHome,
  MoveEnd, PageUp, PageDown, PrintScreen / Pause.
- Punctuation: `=`, `[`, `]`, `\\`, `;`, `/`, backtick.
- Menu (KEYCODE_MENU, the soft-menu / context-menu key on tablets).
- F1–F12.
- Numpad: 0–9 + the four arithmetic ops + dot + Enter + equals.

Keeps the existing `KEYCODE_HOME` (0x03) entry that maps the device
home button to `KeyCode::Home`; in practice that keycode doesn't
reach app input anyway and the new `KEYCODE_MOVE_HOME` (0x7a) maps
to the same variant for the cursor-home case.

Verified on a Pixel Tablet AVD against `is_key_pressed(Escape)`,
`is_key_down(LeftControl)`, and `is_key_pressed(KpEnter)`.

The translation table only covered letters, digits, arrows,
Enter, Tab, Space, Backspace, Shift / Alt, comma + period —
which means a hardware keyboard on Android (tablet + Bluetooth /
USB / Magic Keyboard; ChromeOS; Stage Manager iPad with a Mac
keyboard) couldn't reach the host app with most of its keys.

Adds the keys that have a clear semantic and a matching `KeyCode`
variant:

- Modifiers: Ctrl L/R, Meta L/R (Cmd on Apple keyboards), CapsLock,
  NumLock, ScrollLock. PR not-fl3#403 already wired the `KeyMods` tracking
  for Ctrl / Super, but that's a no-op as long as the keycodes
  themselves translate to `KeyCode::Unknown`.
- Edit cluster: Escape, Insert, Delete (`KEYCODE_FORWARD_DEL`,
  distinct from the existing `KEYCODE_DEL` → Backspace), MoveHome,
  MoveEnd, PageUp, PageDown, PrintScreen / Pause.
- Punctuation: `=`, `[`, `]`, `\\`, `;`, `/`, backtick.
- Menu (KEYCODE_MENU, the soft-menu / context-menu key on tablets).
- F1–F12.
- Numpad: 0–9 + the four arithmetic ops + dot + Enter + equals.

Keeps the existing `KEYCODE_HOME` (0x03) entry that maps the device
home button to `KeyCode::Home`; in practice that keycode doesn't
reach app input anyway and the new `KEYCODE_MOVE_HOME` (0x7a) maps
to the same variant for the cursor-home case.

Verified on a Pixel Tablet AVD against `is_key_pressed(Escape)`,
`is_key_down(LeftControl)`, and `is_key_pressed(KpEnter)`.