Fix ICMP type and code types in application object

[ben-astsec]

Description

This PR makes it so ICMP type/code inside of an application object supports ranges.

Motivation and Context

I was trying to parse a certain configuration and failed because the ICMP type value was a range in there, and I got an error:

ValueError: invalid literal for int() with base 10: '13-14'

This was caused because ApplicationObject.default_icmp_type and ApplicationObject.default_icmp_code had a varty pe="int", even though the configuration can contain ranges.

How Has This Been Tested?

Added a test that makes sure that application objects accept icmp codes/types that are ranges.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.