Improve compatibility with input method that handles repeat prior wl_keyboard version 10

There is a protocol bug for the input_method_v1 protocol, the version of input context grab_keyboard is not correctly associated with the version of wl_keyboard, which makes wl_keyboard may always return a latest version of wl_keyboard and input method may start getting and forwarding REPEAT when they didn't realize that.

Second issue is that whether key repetition need to be generated by input method depending on the focused client, instead of input method itself. If current client's wl_keyboard version is less than 10, there's no point to send key repeat to input method otherwise it shall be just causing inconsistency of the protocol usage between client & input method.

This issue is solved by send repeat info to input method to turn on/off the key repetition on input method side.