plugins: Use translator_st for qemu_plugin_insn_data

plugins: Use translator_st for qemu_plugin_insn_data

Use the bytes that we record for the entire TB, rather than
a per-insn GByteArray.  Record the length of the insn in
plugin_gen_insn_end rather than infering from the length
of the array.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>