backend/s3: Parity with the AWS provider configuration options

[jar-b]

Adds the following arguments to the S3 backend for parity with the AWS Provider.

• custom_ca_bundle
• ec2_metadata_service_endpoint
• ec2_metadata_service_endpoint_mode
• http_proxy
• insecure
• use_fips_endpoint
• use_dualstack_endpoint
• sts_region
• use_path_style (deprecates force_path_style)
• retry_mode

% TF_ACC=1 go test -count=1 ./internal/backend/remote-state/s3/...
ok      github.com/hashicorp/terraform/internal/backend/remote-state/s3 103.942s

Closes #33689
Closes #30444
Closes #30496
Closes #33693
Closes #30491
Closes #33692
Relates #33687

Target Release

1.6.x

Draft CHANGELOG entry

UPGRADE NOTES

• custom_ca_bundle argument and support for the corresponding AWS environment variable, AWS_CA_BUNDLE, for providing custom root and intermediate certificates. (#33689)
• ec2_metadata_service_endpoint and ec2_metadata_service_endpoint_mode arguments and support for the corresponding AWS environment variables, AWS_EC2_METADATA_SERVICE_ENDPOINT and AWS_EC2_METADATA_SERVICE_ENDPOINT_MODE for setting the EC2 metadata service (IMDS) endpoint. The environment variable AWS_METADATA_URL is also supported for compatibility with the AWS provider, but is deprecated. (#30444)
• http_proxy, insecure, use_fips_endpoint, and use_dualstack_endpoint arguments and support for the corresponding environment variables, HTTP_PROXY and HTTPS_PROXY, which enable custom HTTP proxy configurations and the use of alternative AWS endpoints. (#30496)
• sts_region argument to use an alternative region for STS operations. (#33693)
• The force_path_style argument is deprecated in favor of use_path_style for consistency with the AWS SDK. (#30491)
• retry_mode argument and support for the corresponding AWS_RETRY_MODE environment variable to configure how retries are attempted. (#33692)

[ewbankkit]

LGTM 🚀.

% TF_ACC=1 go test -count=1 ./internal/backend/remote-state/s3/...
ok  	github.com/hashicorp/terraform/internal/backend/remote-state/s3	108.948s

[jar-b]

After additional validation functions:

% TF_ACC=1 go test -count=1 ./internal/backend/remote-state/s3/...
ok      github.com/hashicorp/terraform/internal/backend/remote-state/s3 110.781s

[github-actions]

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[github-actions]

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