Make all fields in the deployment schema templatable as `prefect.yaml` step outputs

[kevingrismore]

Describe the current behavior

schedules cannot be provided as deployment step outputs because prefect deploy constructs and validates them before the running of steps and template resolution occurs.

1 validation error for CronSchedule
cron
  Invalid cron string: "{{ get-schedule.schedule }}" (type=value_error)

Describe the proposed behavior

schedules, as well as all other fields on the deployment schema, should be validated after all build and push steps have run and template resolution is completed.

Example Use

A build step where the current workspace is checked to decide which schedule to use.

name: dynamic-schedules
prefect-version: 2.19.7

build:
  - schedules.get_schedule_for_workspace:
      id: get-schedule
  - prefect_docker.deployments.steps.build_docker_image:
      requires: prefect-docker>=0.3.1
      id: build-image
      dockerfile: auto
      image_name: docker.io/kevingrismoreprefect/dynamic-schedules
      tag: '2'

push:
  - prefect_docker.deployments.steps.push_docker_image:
        requires: prefect-docker>=0.3.1
        image_name: '{{ build-image.image_name }}'
        tag: '{{ build-image.tag }}'

pull:
- prefect.deployments.steps.set_working_directory:
    directory: /opt/prefect/

deployments:
- name: dynamic-schedules
  version:
  tags: []
  description:
  entrypoint: flow.py:my_flow
  parameters: {}
  work_pool:
    name: k8s-demo
    work_queue_name:
    job_variables:
      image: '{{ build-image.image }}'
  schedules:
    - cron: '{{ get-schedule.schedule }}'

Additional context

No response