[Tooling] Remove some OpenAPI warning and docker build warning

[tbavelier]

What does this PR do?

• Adds listType=set to 2 monitor options :
  • https://registry.terraform.io/providers/DataDog/datadog/latest/docs/resources/monitor#notify_by
  • https://registry.terraform.io/providers/DataDog/datadog/latest/docs/resources/monitor#renotify_statuses
• Changes as to AS in Operator Dockerfile

Motivation

• Warnings sent when using make generate-openapi / make docker-build :

vscode ➜ /workspaces/datadog-operator (main) $ make generate-openapi
bin/linux-aarch64/openapi-gen --logtostderr=true -o "./" -i ./apis/datadoghq/v1alpha1 -O zz_generated.openapi -p ./apis/datadoghq/v1alpha1 -h ./hack/boilerplate.go.txt -r "-"
API rule violation: list_type_missing,./apis/datadoghq/v1alpha1,DatadogMonitorOptions,NotifyBy
API rule violation: list_type_missing,./apis/datadoghq/v1alpha1,DatadogMonitorOptions,RenotifyStatuses
API rule violation: names_match,./apis/datadoghq/v1alpha1,DatadogMonitorDowntimeStatus,DowntimeID
API rule violation: names_match,./apis/datadoghq/v1alpha1,DatadogMonitorStatus,MonitorStateSyncStatus
bin/linux-aarch64/openapi-gen --logtostderr=true -o "./" -i ./apis/datadoghq/v2alpha1 -O zz_generated.openapi -p ./apis/datadoghq/v2alpha1 -h ./hack/boilerplate.go.txt -r "-"

and

 1 warning found (use docker --debug to expand):
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 2)

Additional Notes

• Following this PR, 2 warnings remain :

API rule violation: names_match,./apis/datadoghq/v1alpha1,DatadogMonitorDowntimeStatus,DowntimeID
API rule violation: names_match,./apis/datadoghq/v1alpha1,DatadogMonitorStatus,MonitorStateSyncStatus

The "required" changes to get rid of these warnings have adverse consequences (e.g. modifying the JSON spec) or symbol renaming, so they're not in scope

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

Describe your test plan

Write there any instructions and details you may have to test your PR.

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.51%. Comparing base (b30f915) to head (bb5b9b7).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1336   +/-   ##
=======================================
  Coverage   47.51%   47.51%           
=======================================
  Files         230      230           
  Lines       22040    22040           
=======================================
  Hits        10472    10472           
  Misses      10976    10976           
  Partials      592      592           

Flag	Coverage Δ
unittests	47.51% <ø> (ø)

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Files	Coverage Δ
apis/datadoghq/v1alpha1/datadogmonitor_types.go	100.00% <ø> (ø)

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