service/elasticache: use waiter and finder function pattern

[gdavison]

Refactors aws_elasticache_cluster, aws_elasticache_replication_group, data.aws_elasticache_cluster, and data.aws_elasticache_replication_group to use waiter and finder functions.

Relates #14959

Release note for CHANGELOG:

NONE

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccAWSElasticacheCluster_\|TestAccAWSElasticacheReplicationGroup_\|TestAccAWSDataElasticacheCluster_\|TestAccDataSourceAwsElasticacheReplicationGroup_'

--- PASS: TestAccAWSElasticacheReplicationGroup_clusteringAndCacheNodesCausesError (66.55s)
--- PASS: TestAccAWSElasticacheCluster_Memcached_FinalSnapshot (71.95s)
--- PASS: TestAccAWSElasticacheCluster_NumCacheNodes_Redis (74.25s)
--- PASS: TestAccAWSDataElasticacheCluster_basic (737.15s)
--- PASS: TestAccAWSElasticacheReplicationGroup_enableSnapshotting (986.85s)
--- PASS: TestAccAWSElasticacheReplicationGroup_updateDescription (987.69s)
--- PASS: TestAccAWSElasticacheReplicationGroup_useCmkKmsKeyId (1090.98s)
--- PASS: TestAccAWSElasticacheCluster_NumCacheNodes_IncreaseWithPreferredAvailabilityZones (1229.45s)
--- PASS: TestAccAWSElasticacheCluster_NodeTypeResize_Memcached (1311.80s)
--- PASS: TestAccAWSElasticacheReplicationGroup_enableAuthTokenTransitEncryption (1396.08s)
--- PASS: TestAccAWSElasticacheReplicationGroup_redisClusterInVpc2 (1420.73s)
--- PASS: TestAccAWSElasticacheReplicationGroup_updateParameterGroup (1485.93s)
--- PASS: TestAccAWSElasticacheCluster_EngineVersion_Redis (1425.75s)
--- PASS: TestAccAWSElasticacheCluster_ReplicationGroupID_SingleReplica (1500.06s)
--- PASS: TestAccAWSElasticacheCluster_NodeTypeResize_Redis (1516.86s)
--- PASS: TestAccAWSElasticacheCluster_ReplicationGroupID_MultipleReplica (1522.45s)
--- PASS: TestAccAWSElasticacheCluster_ReplicationGroupID_AvailabilityZone (1589.59s)
--- PASS: TestAccAWSElasticacheCluster_EngineVersion_Memcached (1528.96s)
--- PASS: TestAccAWSElasticacheReplicationGroup_enableAtRestEncryption (1644.84s)
--- PASS: TestAccAWSElasticacheCluster_AZMode_Redis (662.08s)
--- PASS: TestAccAWSElasticacheCluster_AZMode_Memcached (648.89s)
--- PASS: TestAccAWSElasticacheReplicationGroup_updateMaintenanceWindow (1987.14s)
--- PASS: TestAccDataSourceAwsElasticacheReplicationGroup_NonExistent (10.49s)
--- PASS: TestAccAWSElasticacheCluster_multiAZInVpc (783.12s)
--- PASS: TestAccAWSElasticacheReplicationGroup_NumberCacheClusters (2109.38s)
--- PASS: TestAccAWSElasticacheCluster_vpc (647.27s)
--- PASS: TestAccAWSElasticacheCluster_Port_Redis_Default (521.35s)
--- PASS: TestAccAWSElasticacheReplicationGroup_Uppercase (648.51s)
--- PASS: TestAccAWSElasticacheCluster_ParameterGroupName_Default (673.04s)
--- PASS: TestAccAWSElasticacheReplicationGroup_vpc (789.57s)
--- PASS: TestAccAWSElasticacheCluster_Engine_Memcached (635.77s)
--- PASS: TestAccAWSElasticacheReplicationGroup_multiAzInVpc (917.38s)
--- PASS: TestAccAWSElasticacheReplicationGroup_basic (852.65s)
--- PASS: TestAccAWSElasticacheCluster_Engine_Redis (704.39s)
--- PASS: TestAccAWSElasticacheReplicationGroup_FinalSnapshot (1025.95s)
--- PASS: TestAccAWSElasticacheCluster_Redis_FinalSnapshot (854.12s)
--- PASS: TestAccAWSElasticacheReplicationGroup_NumberCacheClusters_Failover_AutoFailoverDisabled (1541.39s)
--- PASS: TestAccAWSElasticacheCluster_NumCacheNodes_Increase (1074.42s)
--- PASS: TestAccAWSElasticacheCluster_snapshotsWithUpdates (716.36s)
--- PASS: TestAccAWSElasticacheCluster_Port (649.82s)
--- PASS: TestAccAWSElasticacheReplicationGroup_NumberCacheClusters_Failover_AutoFailoverEnabled (2048.20s)
--- PASS: TestAccDataSourceAwsElasticacheReplicationGroup_ClusterMode (1130.27s)
--- PASS: TestAccDataSourceAwsElasticacheReplicationGroup_basic (907.52s)
--- PASS: TestAccAWSElasticacheReplicationGroup_ClusterMode_NonClusteredParameterGroup (827.12s)
--- PASS: TestAccAWSElasticacheReplicationGroup_ClusterMode_Basic (861.43s)
--- PASS: TestAccAWSElasticacheReplicationGroup_updateNodeSize (3047.94s)
--- PASS: TestAccAWSElasticacheReplicationGroup_tags (918.84s)
--- PASS: TestAccAWSElasticacheCluster_NumCacheNodes_Decrease (1120.19s)
--- PASS: TestAccAWSElasticacheReplicationGroup_ClusterMode_NumNodeGroups (4849.48s)

[bflad]

Some minor items, otherwise looks good to me. 🚀

[ghost]

This has been released in version 3.25.0 of the Terraform AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template for triage. Thanks!

[ghost]

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