Reorder reset_arch: parameter forced, elf header, gdb conf (#1004)

Reorder how on reset_architecture fn is going to find arch. Now:
- Param forced
- Elf header
- gdb conf

It is based on chat on #947 with @Grazfather 

This change is needed because if first check for gdb conf if some has
another language active would raise an exception making gef not work at
all (some code match only english sentences).

This pattch would help non englihs users of gdb to not have many
problems to use gef.

Signed-off-by: José Luis Di Biase <josx@interorganic.com.ar>

gef.py

@@ -2150,7 +2150,7 @@ def checksec(filename: str) -> Dict[str, bool]:
     return Elf(filename).checksec
 
 
-@lru_cache()
+@deprecated("Use `gef.arch` instead")
 def get_arch() -> str:
     """Return the binary's architecture."""
     if is_alive():
@@ -3679,20 +3679,22 @@ def reset_architecture(arch: Optional[str] = None) -> None:
             raise OSError(f"Specified arch {arch.upper()} is not supported")
         return
 
-    gdb_arch = get_arch()
-
-    preciser_arch = next((a for a in arches.values() if a.supports_gdb_arch(gdb_arch)), None)
-    if preciser_arch:
-        gef.arch = preciser_arch()
-        return
+    # check for bin running
+    if is_alive():
+        arch = gdb.selected_frame().architecture()
+        gdb_arch = arch.name()
+        preciser_arch = next((a for a in arches.values() if a.supports_gdb_arch(gdb_arch)), None)
+        if preciser_arch:
+            gef.arch = preciser_arch()
+            return
 
     # last resort, use the info from elf header to find it from the known architectures
-    try:
-        arch_name = gef.binary.e_machine if gef.binary else gdb_arch
-        gef.arch = arches[arch_name]()
-    except KeyError:
-        raise OSError(f"CPU type is currently not supported: {get_arch()}")
-    return
+    if gef.binary.e_machine:
+        try:
+            gef.arch = arches[gef.binary.e_machine]()
+        except KeyError:
+            raise OSError(f"CPU type is currently not supported: {gef.binary.e_machine}")
+        return
 
 
 @lru_cache()