Add ValidateOnly params for deployment update API

[kotaroooo0]

Description

cloud-sdk-go do not use validate_only parameter for deployment update api, althouth ElasticCloud's REST API uses it. So, this pull request addressed this issue. reference: https://www.elastic.co/guide/en/cloud-enterprise/current/update-deployment.html#ece_query_parameters_13

Related Issues

https://github.com/elastic/cloud-sdk-go/issues/459

Motivation and Context

cloud-sdk-go do not use validate_only parameter for deployment update api, althouth ElasticCloud's REST API uses it.

How Has This Been Tested?

go 1.21.7 Apple M3 Pro 14.2.1 Local Go script

With ValidateOnly = true parameter, rolling update is not started.

replace package: https://github.com/kotaroooo0/poc-validate-only/blob/main/go.mod#L7 give ValidateOnly parameter: https://github.com/kotaroooo0/poc-validate-only/blob/main/main.go#L25

Types of Changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Refactoring (improves code quality but has no user-facing effect)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation

Readiness Checklist

• [x] My code follows the code style of this project
• [ ] My change requires a change to the documentation
• [ ] I have updated the documentation accordingly
• [ ] I have added tests to cover my changes
• [x] All new and existing tests passed

[tobio]

@kotaroooo0 are you able to amend the commit here so it's signed?

[kotaroooo0]

@tobio is this ok?

[tobio]

Looks great, thanks for following up :)