KEP 1645: add more conflict condition on asymetrical traffic

[MrFreezeex]

• One-line PR description: add more conflict condition on asymetrical traffic

• Issue link: Multi-Cluster Services API #1645

• Other comments:

Make ports raise a conflict when it's not a exact match and a note describing that implementation must not redirect traffic to endpoints from services that actually doesn't declare this port.

Also suggest doing the same for IPFamilies which might have asymmetrical issues. It's merely a suggestion as IPfamilies handling are implementation defined and some implementation may not have issues like that.

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[mikemorris]

Suggested approach makes sense to me and feels less disruptive than changing the guidance from union to intersection.

/lgtm

[zhiying-lin]

LGTM, thank you Arthur!