py/builtinevex: Support passing in a bytearray/buffer to eval/exec.

CPython allows this and it's a simple generalisation of the existing code
which just supported str/bytes.

Fixes issue #5704.

tests/basics/builtin_exec_buffer.py

@@ -0,0 +1,12 @@
+# test builtin exec with a buffer (bytearray/memoryview) input
+
+try:
+    exec
+    bytearray
+    memoryview
+except:
+    print("SKIP")
+    raise SystemExit
+
+exec(bytearray(b'print(1)'))
+exec(memoryview(b'print(2)'))