Fix Redis to Valkey in-place upgrade by handling Engine in ModifyReplicationGroup

[rushmash91]

Fixes: aws-controllers-k8s/community#2299

Description of changes:
fixes the issue where in-place upgrades from ElastiCache Redis to Valkey clusters failed with InvalidParameterCombination: valkey parameter group is not applicable to engine redis. The problem occurred because the ElastiCache controller's custom ModifyReplicationGroup implementation was missing the Engine and CacheParameterGroupName fields in the API request payload, causing AWS to reject Valkey parameter groups being applied to what it perceived as a Redis engine. Additionally, the ModifyReplicationGroup API returns stale field values that don't immediately reflect requested changes, leading the controller to detect false differences and trigger terminal conditions. The solution adds both missing fields to the modify request payload, and normalizes API responses by overriding stale Engine field values with the user's intended values before processing.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ack-prow]

@rushmash91: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
elasticache-verify-attribution	6f4ee3c	link	false	/test elasticache-verify-attribution

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[a-hilaly]

Thanks @rushmash91 !
/lgtm

[ack-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: a-hilaly, rushmash91

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