AP_Landing: stop libraries including AP_Logger.h in .h files

AP_Logger.h is a nexus of includes; while this is being improved over
time, there's no reason for the library headers to include AP_Logger.h
as the logger itself is access by singleton and the structures are in
LogStructure.h

This necessitated moving The PID_Info structure out of AP_Logger's
namespace.  This cleans up a pretty nasty bit - that structure is
definitely not simply used for logging, but also used to pass pid
information around to controllers!

There are a lot of patches in here because AP_Logger.h, acting as a
nexus, was providing transitive header file inclusion in many (some
unlikely!) places.

libraries/AP_Landing/AP_Landing.cpp

@@ -408,7 +408,7 @@ bool AP_Landing::override_servos(void) {
 
 // returns a PID_Info object if there is one available for the selected landing
 // type, otherwise returns a nullptr, indicating no data to be logged/sent
-const AP_Logger::PID_Info* AP_Landing::get_pid_info(void) const
+const AP_PIDInfo* AP_Landing::get_pid_info(void) const
 {
     switch (type) {
 #if HAL_LANDING_DEEPSTALL_ENABLED

libraries/AP_Landing/AP_Landing.h

@@ -109,7 +109,7 @@ public:
     void set_initial_slope(void) { initial_slope = slope; }
     bool is_expecting_impact(void) const;
     void Log(void) const;
-    const AP_Logger::PID_Info * get_pid_info(void) const;
+    const AP_PIDInfo * get_pid_info(void) const;
 
     // landing altitude offset (meters)
     float alt_offset;

libraries/AP_Landing/AP_Landing_Deepstall.cpp

@@ -26,6 +26,7 @@
 #include <SRV_Channel/SRV_Channel.h>
 #include <AP_Common/Location.h>
 #include <AP_AHRS/AP_AHRS.h>
+#include <AP_Logger/AP_Logger.h>
 
 // table of user settable parameters for deepstall
 const AP_Param::GroupInfo AP_Landing_Deepstall::var_info[] = {
@@ -448,13 +449,13 @@ bool AP_Landing_Deepstall::send_deepstall_message(mavlink_channel_t chan) const
     return true;
 }
 
-const AP_Logger::PID_Info& AP_Landing_Deepstall::get_pid_info(void) const
+const AP_PIDInfo& AP_Landing_Deepstall::get_pid_info(void) const
 {
     return ds_PID.get_pid_info();
 }
 
 void AP_Landing_Deepstall::Log(void) const {
-    const AP_Logger::PID_Info& pid_info = ds_PID.get_pid_info();
+    const AP_PIDInfo& pid_info = ds_PID.get_pid_info();
     struct log_DSTL pkt = {
         LOG_PACKET_HEADER_INIT(LOG_DSTL_MSG),
         time_us          : AP_HAL::micros64(),

libraries/AP_Landing/AP_Landing_Deepstall.h

@@ -100,7 +100,7 @@ private:
 
     bool send_deepstall_message(mavlink_channel_t chan) const;
 
-    const AP_Logger::PID_Info& get_pid_info(void) const;
+    const AP_PIDInfo& get_pid_info(void) const;
 
     //private helpers
     void build_approach_path(bool use_current_heading);

libraries/AP_Landing/AP_Landing_Slope.cpp

@@ -23,6 +23,7 @@
 #include <AP_LandingGear/AP_LandingGear.h>
 #include <AP_AHRS/AP_AHRS.h>
 #include <AP_GPS/AP_GPS.h>
+#include <AP_Logger/AP_Logger.h>
 
 void AP_Landing::type_slope_do_land(const AP_Mission::Mission_Command& cmd, const float relative_altitude)
 {