[PATCH 1/2] gdb: use inferior::threads instead of all_threads and a PID filter

I noticed a few places where we iterated over `all_threads ()` but
then immediately filtered by PID.  It would be better to instead
iterate over `inferior::threads ()` and remove the PID filtering.

These should be equivalent as a single inferior should contain every
thread with a given PID, and should only contain threads with that
given PID.

While editing the `for (...)` loops I have replaced 'auto' with
'thread_info' for additional type clarity.

There should be no user visible changes after this commit.
---
 gdb/mi/mi-main.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 8b6da41ffeb..903c6a5f411 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -359,14 +359,11 @@ mi_cmd_exec_interrupt (const char *command, const char *const *argv, int argc)
       scoped_disable_commit_resumed disable_commit_resumed
 	("interrupting all threads of thread group");
 
-      for (auto &thread : all_threads ())
+      for (thread_info &thread : inf->threads ())
 	{
 	  if (thread.state () != THREAD_RUNNING)
 	    continue;
 
-	  if (thread.ptid.pid () != inf->pid)
-	    continue;
-
 	  target_stop (thread.ptid);
 	}
     }
@@ -603,14 +600,13 @@ print_one_inferior (struct inferior *inferior, bool recurse,
 
       if (inferior->pid != 0)
 	{
-	  for (auto &ti : all_threads ())
-	    if (ti.ptid.pid () == inferior->pid)
-	      {
-		int core = target_core_of_thread (ti.ptid);
+	  for (thread_info &ti : inferior->threads ())
+	    {
+	      int core = target_core_of_thread (ti.ptid);
 
-		if (core != -1)
-		  cores.insert (core);
-	      }
+	      if (core != -1)
+		cores.insert (core);
+	    }
 	}
 
       if (!cores.empty ())
-- 
2.25.4