[bug]: perpdiff duplicate tags

[johnsonaj]

Description

When duplicate tags are moved from from tags to default_tags, and vice versa, the state fails to update correctly. This causes a perpetual diff.

Relations

Closes #31695

References

Output from Acceptance Testing

$ make testacc TESTARGS='-run=TestAccVPC_ -short' PKG=vpc

==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/ec2/... -v -count 1 -parallel 20  -run=TestAccVPC_ -short -timeout 180m
    vpc_test.go:1015: skipping long-running test in short mode
--- SKIP: TestAccVPC_IPAMIPv4BasicNetmask (0.00s)
    vpc_test.go:1042: skipping long-running test in short mode
--- SKIP: TestAccVPC_IPAMIPv4BasicExplicitCIDR (0.00s)
    vpc_test.go:1070: skipping long-running test in short mode
--- SKIP: TestAccVPC_IPAMIPv6 (0.00s)
=== NAME  TestAccVPC_assignGeneratedIPv6CIDRBlockWithNetworkBorderGroup
    ec2_availability_zone_data_source_test.go:219: skipping since no Local Zones are available
--- SKIP: TestAccVPC_assignGeneratedIPv6CIDRBlockWithNetworkBorderGroup (1.05s)
--- PASS: TestAccVPC_disappears (39.96s)
--- PASS: TestAccVPC_DefaultTagsProviderAndResource_duplicateTag (43.17s)
--- PASS: TestAccVPC_tags_null (44.91s)
--- PASS: TestAccVPC_tags_computed (46.10s)
--- PASS: TestAccVPC_basic (54.50s)
--- PASS: TestAccVPC_enableNetworkAddressUsageMetrics (64.78s)
--- PASS: TestAccVPC_disabledDNSSupport (65.09s)
--- PASS: TestAccVPC_bothDNSOptionsSet (64.32s)
--- PASS: TestAccVPC_DefaultTags_updateToResourceOnly (77.44s)
--- PASS: TestAccVPC_DefaultTags_updateToProviderOnly (78.58s)
--- PASS: TestAccVPC_DynamicResourceTags_ignoreChanges (79.03s)
--- PASS: TestAccVPC_defaultAndIgnoreTags (82.45s)
--- PASS: TestAccVPC_updateDNSHostnames (83.52s)
--- PASS: TestAccVPC_DefaultTags_zeroValue (91.08s)
--- PASS: TestAccVPC_DefaultTagsProviderAndResource_overlappingTag (91.80s)
--- PASS: TestAccVPC_DefaultTagsProviderAndResource_moveDuplicateTags (92.47s)
--- PASS: TestAccVPC_DefaultTags_providerOnlyTestAccVPC_DefaultTags_providerOnly (93.20s)
--- PASS: TestAccVPC_DefaultTagsProviderAndResource_nonOverlappingTag (95.36s)
--- PASS: TestAccVPC_DynamicResourceTagsMergedWithLocals_ignoreChanges (58.45s)
--- PASS: TestAccVPC_tags (98.73s)
--- PASS: TestAccVPC_ignoreTags (57.67s)
--- PASS: TestAccVPC_tenancy (75.30s)
--- PASS: TestAccVPC_assignGeneratedIPv6CIDRBlock (119.43s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/ec2	122.660s

[github-actions]

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