Use accessor methods for AWS SDK API clients

[ewbankkit]

Description

Generate and use accessor methods instead of fields for AWS API clients in conns.AWSClient.

Relations

Closes #28488.

Output from Acceptance Testing

% make testacc TESTARGS='-run=TestAccEC2EBSVolume_finalSnapshot\|TestAccEC2Instance_EBSBlockDevice_RootBlockDevice_removed' PKG=ec2 ACCTEST_PARALLELISM=3
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/ec2/... -v -count 1 -parallel 3  -run=TestAccEC2EBSVolume_finalSnapshot\|TestAccEC2Instance_EBSBlockDevice_RootBlockDevice_removed -timeout 180m
=== RUN   TestAccEC2EBSVolume_finalSnapshot
=== PAUSE TestAccEC2EBSVolume_finalSnapshot
=== RUN   TestAccEC2Instance_EBSBlockDevice_RootBlockDevice_removed
=== PAUSE TestAccEC2Instance_EBSBlockDevice_RootBlockDevice_removed
=== CONT  TestAccEC2EBSVolume_finalSnapshot
=== CONT  TestAccEC2Instance_EBSBlockDevice_RootBlockDevice_removed
--- PASS: TestAccEC2EBSVolume_finalSnapshot (64.30s)
--- PASS: TestAccEC2Instance_EBSBlockDevice_RootBlockDevice_removed (143.40s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/ec2	148.641s

[github-actions]

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[github-actions]

This functionality has been released in v4.49.0 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. Thank you!

[github-actions]

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