Delay GDB server launch until emulator run

[Daniel-Valentine]

This PR shifts a few lines of code to delay the GDB server from running until the emulator itself actually begins.

As it stands the GDB server starts and awaits connections as soon as RPCS3 is launched but before any emulation. Attempting to attach GDB will cause RPCS3 to segfault by deferencing a nullptr, specifically th in the command parser functions, because select_thread wasn't able to select a thread and left the selected_thread pointer empty, because the CPU isn't running.

Example GDB trace of the segmentation fault:

Thread 5 "GDBDebugger" received signal SIGSEGV, Segmentation fault.
[snip]
0x0000000000df0670 in GDBDebugServer::cmd_read_all_registers(gdb_cmd&) ()
(gdb) backtrace
#0  0x0000000000df0670 in GDBDebugServer::cmd_read_all_registers(gdb_cmd&) ()
#1  0x0000000000df1c54 in GDBDebugServer::on_task() ()
#2  0x0000000000dffbc1 in task_stack::task_type<named_thread::start_thread(std::shared_ptr<void> const&)::{lambda()#1}>::invoke() ()
#3  0x0000000000e02baa in thread_ctrl::start(std::shared_ptr<thread_ctrl> const&, task_stack)::{lambda(void*)#1}::_FUN(void*) ()
[snip]

which corresponds to one of the first invoked commands

rpcs3/Utilities/GDBDebugServer.cpp

Lines 585 to 591 in c09c792

	bool GDBDebugServer::cmd_read_all_registers(gdb_cmd & cmd)
	{
	std::string result;
	select_thread(general_ops_thread_id);
	auto th = selected_thread.lock();
	if (th->id_type() == 1) {

[elad335]

using LOG_SUCCESS is fine

[elad335]

no need in "HERE"

[AniLeo]

Needs rebasing and squashing