`hostname` should not be required in `HTTPActiveHealthChecker`

[muwaqar]

Description:
hostname is marked as required in the HTTPActiveHealthChecker: https://gateway.envoyproxy.io/latest/api/extension_types/#httpactivehealthchecker

this should be optional, as the doc mentions the default behavior:

Default: HTTPRoute or GRPCRoute hostname.

Repro steps:

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Environment:

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Logs:

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[arkodg]

missing the optional tag

gateway/api/v1alpha1/healthcheck_types.go

Line 157 in 402cd99

// +kubebuilder:validation:Pattern=`^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$`

[yyadavalli]

/assign