tcg: Rename TEMP_LOCAL to TEMP_TB

Use TEMP_TB as that is more explicit about the default
lifetime of the data.  While "global" and "local" used
to be contrasting, we have more lifetimes than that now.

Do not yet rename tcg_temp_local_new_*, just the enum.

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