resource/aws_security_group: Use default VPC when no VPC ID passed

[gdavison]

When no vpc_id is passed to aws_security_group, use the default VPC to match the behaviour of the AWS API.

Relates #26525
Relates #26666
Relates #23625

Output from acceptance testing:

$ make testacc PKG=ec2 TESTS=TestAccVPCSecurityGroup_

--- PASS: TestAccVPCSecurityGroup_invalidCIDRBlock (9.83s)
--- PASS: TestAccVPCSecurityGroup_namePrefix (88.38s)
--- PASS: TestAccVPCSecurityGroup_ipv6 (90.89s)
--- PASS: TestAccVPCSecurityGroup_self (93.06s)
--- PASS: TestAccVPCSecurityGroup_basic (93.14s)
--- PASS: TestAccVPCSecurityGroup_allowAll (93.43s)
--- PASS: TestAccVPCSecurityGroup_defaultEgressVPC (93.89s)
--- PASS: TestAccVPCSecurityGroup_vpc (95.51s)
--- PASS: TestAccVPCSecurityGroup_sourceSecurityGroup (97.19s)
--- PASS: TestAccVPCSecurityGroup_ipRangeAndSecurityGroupWithSameRules (100.59s)
--- PASS: TestAccVPCSecurityGroup_ingressWithCIDRAndSGsVPC (103.11s)
--- PASS: TestAccVPCSecurityGroup_cidrAndGroups (105.65s)
--- PASS: TestAccVPCSecurityGroup_multiIngress (105.65s)
--- PASS: TestAccVPCSecurityGroup_egressWithPrefixList (114.39s)
--- PASS: TestAccVPCSecurityGroup_ruleGathering (117.20s)
--- PASS: TestAccVPCSecurityGroup_change (136.03s)
--- PASS: TestAccVPCSecurityGroup_namePrefixTerraform (68.74s)
--- PASS: TestAccVPCSecurityGroup_vpcProtoNumIngress (67.09s)
--- PASS: TestAccVPCSecurityGroup_vpcNegOneIngress (66.90s)
--- PASS: TestAccVPCSecurityGroup_failWithDiffMismatch (58.01s)
--- PASS: TestAccVPCSecurityGroup_driftComplex (72.95s)
--- PASS: TestAccVPCSecurityGroup_ingressMode (170.21s)
--- PASS: TestAccVPCSecurityGroup_egressMode (172.46s)
--- PASS: TestAccVPCSecurityGroup_tags (170.21s)
--- PASS: TestAccVPCSecurityGroup_ipRangesWithSameRules (62.89s)
--- PASS: TestAccVPCSecurityGroup_ipv4AndIPv6Egress (69.32s)
--- PASS: TestAccVPCSecurityGroup_nameTerraformPrefix (56.87s)
--- PASS: TestAccVPCSecurityGroup_rulesDropOnError (103.10s)
--- PASS: TestAccVPCSecurityGroup_RuleLimit_cidrBlockExceededAppend (104.97s)
--- PASS: TestAccVPCSecurityGroup_disappears (39.89s)
--- PASS: TestAccVPCSecurityGroup_noVPC (45.66s)
--- PASS: TestAccVPCSecurityGroup_nameGenerated (49.06s)
--- PASS: TestAccVPCSecurityGroup_ruleDescription (126.07s)
--- PASS: TestAccVPCSecurityGroup_ingressWithPrefixList (58.58s)
--- PASS: TestAccVPCSecurityGroup_RuleLimit_exceededAppend (129.34s)
--- PASS: TestAccVPCSecurityGroup_RuleLimit_exceededAllNew (126.46s)
--- PASS: TestAccVPCSecurityGroup_RuleLimit_exceededPrepend (125.52s)
--- PASS: TestAccVPCSecurityGroup_forceRevokeRulesTrue (403.84s)
--- PASS: TestAccVPCSecurityGroup_emrDependencyViolation (845.93s)
--- PASS: TestAccVPCSecurityGroup_forceRevokeRulesFalse (1149.34s)

[ewbankkit]

Suggested change

	resource/aws_security_group: Defaults to default VPC when not supplied
	resource/aws_security_group: `vpc_id` defaults to the AWS Region's default VPC when not configured

[ewbankkit]

LGTM 🚀.

% make testacc TESTARGS='-run=TestAccVPCSecurityGroup_noVPC\|TestAccVPCSecurityGroup_basic' PKG=ec2 ACCTEST_PARALLELISM=2
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/ec2/... -v -count 1 -parallel 2  -run=TestAccVPCSecurityGroup_noVPC\|TestAccVPCSecurityGroup_basic -timeout 180m
=== RUN   TestAccVPCSecurityGroup_basic
=== PAUSE TestAccVPCSecurityGroup_basic
=== RUN   TestAccVPCSecurityGroup_noVPC
=== PAUSE TestAccVPCSecurityGroup_noVPC
=== CONT  TestAccVPCSecurityGroup_basic
=== CONT  TestAccVPCSecurityGroup_noVPC
--- PASS: TestAccVPCSecurityGroup_basic (26.03s)
--- PASS: TestAccVPCSecurityGroup_noVPC (42.56s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/ec2	46.515s

[github-actions]

This functionality has been released in v4.30.0 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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