fix(mavlink): remove all stale mavlink_tests references

The mavlink_tests module was deleted in 1009268d31 but several
references were left behind, breaking builds on all targets.

Removed:
- CMakeLists.txt: add_subdirectory(mavlink_tests)
- mavlink_ftp.cpp: #include of deleted mavlink_ftp_test.h
- mavlink_ftp.h: MavlinkFtpTest forward decl and friend class
- posix-configs/SITL/init/test/test_mavlink: dead init script
- sitl_tests.cmake: sitl-mavlink CTest target
- install-voxl.sh: px4-mavlink_tests symlink

Ref: https://github.com/PX4/PX4-Autopilot/issues/26738
Signed-off-by: Ramon Roche <mrpollo@gmail.com>

src/modules/mavlink/CMakeLists.txt

@@ -145,10 +145,6 @@ px4_add_module(
 	UNITY_BUILD
 	)
 
-if(PX4_TESTING)
-	add_subdirectory(mavlink_tests)
-endif()
-
 px4_add_unit_gtest(SRC MavlinkStatustextHandlerTest.cpp
 	INCLUDES
 		${MAVLINK_LIBRARY_DIR}

src/modules/mavlink/mavlink_ftp.cpp

@@ -43,8 +43,6 @@
 #include <cstring>
 
 #include "mavlink_ftp.h"
-#include "mavlink_tests/mavlink_ftp_test.h"
-
 #include "mavlink_main.h"
 
 using namespace time_literals;

src/modules/mavlink/mavlink_ftp.h

@@ -45,7 +45,6 @@
 
 #include "mavlink_bridge_header.h"
 
-class MavlinkFtpTest;
 class Mavlink;
 
 /// MAVLink remote file server. Support FTP like commands using MAVLINK_MSG_ID_FILE_TRANSFER_PROTOCOL message.
@@ -199,8 +198,5 @@ private:
 	uint8_t _last_reply[MAVLINK_MSG_ID_FILE_TRANSFER_PROTOCOL_LEN - MAVLINK_MSG_FILE_TRANSFER_PROTOCOL_FIELD_PAYLOAD_LEN
 								      + sizeof(PayloadHeader) + sizeof(uint32_t)];
 
-	// Mavlink test needs to be able to call send
-	friend class MavlinkFtpTest;
-
 	int _our_errno {0};
 };