feat: add support to specify FIS network actions

[maintux]

Description

I added the Subnets target type to the FIS validator in order to use the Network Actions.

References

https://docs.aws.amazon.com/fis/latest/userguide/fis-actions-reference.html#network-actions-reference

[github-actions]

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[johnsonaj]

LGTM 🚀

$ make testacc TESTARGS='-run=TestAccFISExperimentTemplate_' PKG=fis

==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/fis/... -v -count 1 -parallel 20  -run=TestAccFISExperimentTemplate_ -timeout 180m
--- PASS: TestAccFISExperimentTemplate_disappears (14.53s)
--- PASS: TestAccFISExperimentTemplate_spot (14.58s)
--- PASS: TestAccFISExperimentTemplate_basic (16.76s)
--- PASS: TestAccFISExperimentTemplate_update (26.04s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/fis	29.116s

[johnsonaj]

@maintux thanks for the contribution! 🎉

[github-actions]

This functionality has been released in v4.64.0 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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