rename cloudName to name

[car-roll]

cc @res0nance
Preparing for jenkinsci/jenkins#8310 where cloud name changes will be done on a separate page

The use of the variable name cloudName in AmazonEC2Cloud forces jenkins core to have a special case of handling cloudName when it not a variable of Cloud.
https://github.com/jenkinsci/jenkins/blob/d41b0f5807923286ad33d4847af95e2c6c7c77ba/core/src/main/java/jenkins/agents/CloudSet.java#L229

Also changed AmazonEC2CloudTest.testSshKeysCredentialsIdRemainsUnchangedAfterUpdatingOtherFields to modify a different field.

Testing done

manually created new AmazonEC2Cloud

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5. Link to relevant pull requests, esp. upstream and downstream changes
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[basil]

Similar issue also exists in the integration tests for configuration-as-code-plugin

[car-roll]

CI issues

[car-roll]

Closing in favor of a less invasive change