Add seperate fields for configuring autoscaler scale-up and scale-down

[jrhouston]

Description

This PR adds separate fields so that the cooldown period can be controlled separately for scaling up and scaling down.

Tests

• https://github.com/hashicorp/terraform-cloud-operator/actions/runs/10089414062
• https://github.com/hashicorp/terraform-cloud-operator/actions/runs/10089415020
• https://github.com/hashicorp/terraform-cloud-operator/actions/runs/10089415953
• https://github.com/hashicorp/terraform-cloud-operator/actions/runs/10089417015

Usage Example

apiVersion: app.terraform.io/v1alpha2
kind: AgentPool
metadata:
  name: this
spec:
  name: this
  organization: kubernetes-operator
  token:
    secretKeyRef:
      name: tfc-operator
      key: token
  agentTokens:
    - name: alpha
  autoscaling:
    maxReplicas: 4
    minReplicas: 0
    cooldownPeriod:
      scaleUpSeconds: 30
      scaleDownSeconds: 1800
  agentDeployment:
    replicas: 0

References

• Closes 🚀 AgentPool has separate levers for cooldownPeriodSeconds and scalingPeriodSeconds #341
• JIRA: TFECO-5803

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[arybolovlev]

Thanks! 🚀 I will wait for tests to pass and then merge this change.