Offer Rename / Kill when long pressing a session in the drawer

[kedimuzafer]

Long pressing a session in the drawer goes straight to renaming it, so there is no way to close a
session from the drawer at all. Killing one means switching to it first and using the terminal's own
context menu, or typing exit.

This makes long press open a two item dialog offering Rename and Kill. Rename keeps the
existing behaviour; Kill reuses the same confirmation prompt (title_confirm_kill_session) before
calling finishIfRunning() and removing the finished session, matching what the terminal context
menu already does.

Two strings are added for the menu items and one for the confirmation.

Tested on an Android 16 device and an API 31 emulator: renaming still works, killing removes the
session from the drawer list, and cancelling leaves it running.

[kedimuzafer]

Pushed a fix for two problems in the original commit, found while using it.

Killing a running session did not remove it. finishIfRunning() only sends SIGKILL; the process exits asynchronously, and TermuxSession.finish() returns early for a session that is still running, so calling removeFinishedSession() in the same breath silently did nothing. An already exited session was removed fine, which hid the bug.

The removal is now deferred to onSessionFinished() through a new killAndRemoveSession(). Sessions that exit on their own take the existing path unchanged, and the auto-close rule for exit codes 0 and 130 is untouched.

The confirmation dialog was unreadable. It was built with androidx.appcompat.app.AlertDialog, which picks up the activity theme; Theme.TermuxActivity.DayNight.NoActionBar sets a black window background, so the buttons ended up dark on dark. Switched to android.app.AlertDialog, which is what showKillSessionDialog() and TextInputDialogUtils already use.