Feat(eos_designs): Enhance isis authentication support

The more I read the more I think we will need to revisit all this ISIS authentication at some point:

From our doc (https://www.arista.com/en/um-eos/eos-is-is#xx1232672):

• It seems today in eos_designs we only support this TOI: https://www.arista.com/en/support/toi/eos-4-15-2f/13687-isis-md5
• our keys are not able to discriminate between levels from eos_designs
• There is no mention of using SHA which is described here (and supported by our filters): cf this TOI: https://www.arista.com/en/support/toi/eos-4-21-3f/14126-is-is-authentication-using-sha
• and recently this was introduced with shared-secret: https://www.arista.com/en/support/toi/eos-4-30-0f/17486-support-for-hitless-authentication-key-rollover-for-is-is
• [interesting recommendation]: To maximize interoperability, Arista recommends using the same key in both interface mode and in the router isis mode.

[!NOTE] eos_cli_config_gen supports all this.

Originally posted by @gmuloc in https://github.com/aristanetworks/avd/issues/5571#issuecomment-3052832905