exec: Declare CPUBreakpoint/CPUWatchpoint type in 'breakpoint.h' header

The CPUBreakpoint and CPUWatchpoint structures are declared
in "hw/core/cpu.h", which contains declarations related to
CPUState and CPUClass. Some source files only require the
BP/WP definitions and don't need to pull in all CPU* API.
In order to simplify, create a new "exec/breakpoint.h" header.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20240418192525.97451-3-philmd@linaro.org>
5 files changed