feat(admission): enable hpa for KAI Admission Service

[faizan-exe]

Description

This PR enables Horizontal Pod Autoscaling for Admission Pods. Previously, user can only specifiy fixed number of replicas for admission pods using kai-config.yaml - now they have the option to enable autoscaling and avoid manual configuration.

The metric for autoscaling is controller_runtime_webhook_requests_in_flight.

Prometheus Adapter is also introduced for interacting with Custom Metrics API.

Related Issues

Issue #901

Checklist

• [Yes] Self-reviewed
• [Yes] Added/updated tests (if needed)
• [Yes] Updated documentation (if needed)

Breaking Changes

No breaking changes. Backward Compatibility is being ensured.

[github-actions]

Merging this branch changes the coverage (1 decrease, 1 increase)

Impacted Packages	Coverage Δ	🤖
github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission	20.37% (-0.68%)	👎
github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission	87.77% (+0.57%)	👍

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission/admission.go	100.00% (ø)	22 (+6)	22 (+6)	0
github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission/zz_generated.deepcopy.go	0.00% (ø)	86 (+26)	0	86 (+26)
github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission/admission.go	72.00% (ø)	25	18	7
github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission/resources.go	91.23% (+0.23%)	114 (+14)	104 (+13)	10 (+1)	👍

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission/admission_test.go
• github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission/resources_test.go

[github-actions]

Merging this branch changes the coverage (1 decrease, 1 increase)

Impacted Packages	Coverage Δ	🤖
github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission	20.37% (-0.68%)	👎
github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission	87.77% (+0.57%)	👍

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission/admission.go	100.00% (ø)	22 (+6)	22 (+6)	0
github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission/zz_generated.deepcopy.go	0.00% (ø)	86 (+26)	0	86 (+26)
github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission/admission.go	72.00% (ø)	25	18	7
github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission/resources.go	91.23% (+0.23%)	114 (+14)	104 (+13)	10 (+1)	👍

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/NVIDIA/KAI-scheduler/pkg/apis/kai/v1/admission/admission_test.go
• github.com/NVIDIA/KAI-scheduler/pkg/operator/operands/admission/resources_test.go