Refactored alert tests

[AWSHurneyt]

Description

Updated alert creation following opensearch-project/common-utils#584.

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[AWSHurneyt]

./gradlew build passes locally once PRs opensearch-project/common-utils#584 and opensearch-project/alerting#1404 were published to my local maven repo.

./gradlew build
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OpenSearch Build Hamster says Hello!
  Gradle Version        : 8.5
  OS Info               : Linux 5.10.205-172.807.amzn2int.x86_64 (amd64)
  JDK Version           : 14 (Oracle JDK)
  JAVA_HOME             : /local/home/hurneyt/jdk-14.0.2
  Random Testing Seed   : E024BEE087D93140
  In FIPS 140 mode      : false
=======================================

Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0.

You can use '--warning-mode all' to show the individual deprecation warnings and determine if they come from your own scripts or plugins.

For more on this, please refer to https://docs.gradle.org/8.5/userguide/command_line_interface.html#sec:command_line_warnings in the Gradle documentation.

BUILD SUCCESSFUL in 14m 20s
30 actionable tasks: 10 executed, 20 up-to-date