Use better approach to signal remote process' exit status

1. `remote_info.failed_process` stores symbol but we only use the value's
   presence to check if the process is force-killed.
2. The force-killed status is directly controlled by `kill_safely` through
    `kill_remote_debuggee`, which is directly called right before we check
    the status with `remote_info.failed_process`.

Combining the two, we can just let `kill_safely` and `kill_remote_debuggee` to
return the force-killed status and not storing it in `remote_info`, which
already contains a bunch of information.

This also eliminates the need to pass `test_info` to `kill_safely`, which
makes related code easier to understand and maintain.

Author: st0012

test/support/console_test_case.rb

@@ -200,7 +200,7 @@ def run_test_scenario cmd, test_info
           # kill debug console process
           read.close
           write.close
-          kill_safely pid, :debugger, test_info
+          kill_safely pid
         end
       end
     end

test/support/protocol_test_case.rb

@@ -338,8 +338,7 @@ def execute_dap_scenario scenario
       is_assertion_failure = true
       raise e
     ensure
-      kill_remote_debuggee test_info
-      if test_info.failed_process && !is_assertion_failure
+      if kill_remote_debuggee(test_info) && !is_assertion_failure
         flunk create_protocol_message "Expected the debuggee program to finish"
       end
       # Because the debuggee may be terminated by executing the following operations, we need to run them after `kill_remote_debuggee` method.
@@ -372,8 +371,7 @@ def execute_cdp_scenario_ scenario
       is_assertion_failure = true
       raise e
     ensure
-      kill_remote_debuggee test_info
-      if test_info.failed_process && !is_assertion_failure
+      if kill_remote_debuggee(test_info) && !is_assertion_failure
         flunk create_protocol_message "Expected the debuggee program to finish"
       end
       # Because the debuggee may be terminated by executing the following operations, we need to run them after `kill_remote_debuggee` method.

test/support/test_case.rb

@@ -122,16 +122,18 @@ def wait_pid pid, sec
       true
     end
 
-    def kill_safely pid, name, test_info
-      return if wait_pid pid, TIMEOUT_SEC
+    def kill_safely pid
+      needs_kill = false
+      return needs_kill if wait_pid pid, TIMEOUT_SEC
 
-      test_info.failed_process = name
+      needs_kill = true
 
       Process.kill :TERM, pid
-      return if wait_pid pid, 0.2
+      return needs_kill if wait_pid pid, 0.2
 
       Process.kill :KILL, pid
       Process.waitpid(pid)
+      needs_kill
     rescue Errno::EPERM, Errno::ESRCH
     end
 
@@ -142,13 +144,15 @@ def check_error(error, test_info)
     end
 
     def kill_remote_debuggee test_info
-      return unless r = test_info.remote_info
+      needs_kill = false
+      return needs_kill unless r = test_info.remote_info
 
-      kill_safely r.pid, :remote, test_info
+      needs_kill = kill_safely r.pid
       r.reader_thread.kill
       # Because the debuggee may be terminated by executing the following operations, we need to run them after `kill_safely` method.
       r.r.close
       r.w.close
+      needs_kill
     end
 
     def setup_remote_debuggee(cmd)