resource/aws_subnet: Add List support

[gdavison]

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the library.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

Description

Adds List support for aws_subnet

Output from Acceptance Testing

% make testacc PKG=ec2 TESTS=TestAccVPCSubnet_List_

--- PASS: TestAccVPCSubnet_List_ExcludeDefaultSubnets (51.33s)
--- PASS: TestAccVPCSubnet_List_SubnetIDs (52.10s)
--- PASS: TestAccVPCSubnet_List_FilteredSubnetIDs (54.28s)
--- PASS: TestAccVPCSubnet_List_Basic (54.29s)
--- PASS: TestAccVPCSubnet_List_Filtered (54.29s)
--- PASS: TestAccVPCSubnet_List_RegionOverride (55.75s)

[github-actions]

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[jar-b]

LGTM 🎉

% make t K=ec2 T=TestAccVPCSubnet_List_
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
make: Running acceptance tests on branch: 🌿 f-list-subnets 🌿...
TF_ACC=1 go1.24.8 test ./internal/service/ec2/... -v -count 1 -parallel 20 -run='TestAccVPCSubnet_List_'  -timeout 360m -vet=off
go: downloading github.com/hashicorp/terraform-plugin-testing v1.14.0-beta.1.0.20251013071646-7ed2ee242705
2025/10/16 11:03:28 Creating Terraform AWS Provider (SDKv2-style)...
2025/10/16 11:03:29 Initializing Terraform AWS Provider (SDKv2-style)...

    vpc_subnet_list_test.go:438: Skipping because ExpectError is not currently supported for Query mode
--- SKIP: TestAccVPCSubnet_List_Filtered_DefaultForAZ (0.00s)
--- PASS: TestAccVPCSubnet_List_ExcludeDefaultSubnets (18.17s)
--- PASS: TestAccVPCSubnet_List_Basic (19.58s)
--- PASS: TestAccVPCSubnet_List_Filtered (19.59s)
--- PASS: TestAccVPCSubnet_List_FilteredSubnetIDs (19.92s)
--- PASS: TestAccVPCSubnet_List_SubnetIDs (21.88s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/ec2        28.852s

[github-actions]

Warning

This Issue has been closed, meaning that any additional comments are much easier for the maintainers to miss. Please assume that the maintainers will not see them.

Ongoing conversations amongst community members are welcome, however, the issue will be locked after 30 days. Moving conversations to another venue, such as the AWS Provider forum, is recommended. If you have additional concerns, please open a new issue, referencing this one where needed.

[github-actions]

This functionality has been released in v6.17.0 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!