tests/extmod/ubinascii: Add tests for bytes.hex etc.

Also make the sep test not micropython-specific.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

tests/basics/builtin_str_hex.py

@@ -0,0 +1,24 @@
+if not hasattr(bytes, "fromhex"):
+    print("SKIP")
+    raise SystemExit
+
+for x in (
+    b"\x00\x01\x02\x03\x04\x05\x06\x07",
+    b"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
+    b"\x7f\x80\xff",
+    b"1234ABCDabcd",
+):
+    print(x.hex())
+    print(bytearray(x).hex())
+    print(memoryview(x).hex())
+    print(x.hex(":"))
+    print(bytearray(x).hex(":"))
+    print(memoryview(x).hex(":"))
+
+for x in (
+    "0001020304050607",
+    "08090a0b0c0d0e0f",
+    "7f80ff",
+    "313233344142434461626364",
+):
+    print(bytes.fromhex(x))