feat: Add support for running scripted probes

[notheotherben]

This PR adds support for writing !Script probes which run a predefined JavaScript probe, allowing substantially more complex probe execution models to be implemented (including interactive request/response flows, multi-stage operations, or the use of dynamic authentication in a managed service identity environment).

This functionality is built on top of Deno and can be used with a probe definition like the following:

probes:
  - name: bender.production.script
    policy:
      interval: 60000
      timeout: 5000
      retries: 2
    target: !Script
      args:
        - https://bender.sierrasoftworks.com
      code: |
        const resp = await fetch(`${Deno.args[0]}/api/v1/quote/bender`, {
          headers: {
            "Accept": "application/json",
            ...getTraceHeaders()
          }
        })

        setOutput("http.status", resp.status)

        if (resp.ok) {
          const quote = await resp.json()
          setOutput("quote.who", quote.who)
        }

    validators:
      http.status: !Equals 200
      quote.who: !Equals "Bender"

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Azure Static Web Apps: Your stage site is ready! Visit it here: https://red-coast-03f9f2c03-120.westeurope.1.azurestaticapps.net

[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://red-coast-03f9f2c03-120.westeurope.1.azurestaticapps.net