CUSTESC-29915: unify output for rules without rule settings

[alyssamw]

Closes #2085

[github-actions]

changelog detected ✅

[jacobbednarz]

thanks for the PR here @alyssamw. i went ahead and pushed a couple of commits to address some issues i found here. details are in the commits but at a high level:

• i moved the empty logic into the flattenTeamsRuleSettings method for two reasons. the first is that Read/Create need to use the same source for when to save the nested object in state. the second part is that we always want to call d.Set (regardless of whether we have values) to make sure we can clear the state if someone removes the values.
• i extended the test logic to cover the second part of the first point but also found a logic bug in the empty logic where a != nil should have been a == nil.

ideally, we'd want to revisit some of these structs in cloudflare-go and better utilise pointers and omitempty to handle some of the falsey style checks we are currently aggregating to make it a bit easier to determine when something has been unset.

acceptance tests are now passing

TF_ACC=1 go test ./internal/sdkv2provider -v -run "^TestAccCloudflareTeamsRule_" -count 1 -timeout 120m -parallel 1
=== RUN   TestAccCloudflareTeamsRule_Basic
--- PASS: TestAccCloudflareTeamsRule_Basic (14.99s)
=== RUN   TestAccCloudflareTeamsRule_NoSettings
--- PASS: TestAccCloudflareTeamsRule_NoSettings (21.98s)
PASS
ok  	github.com/cloudflare/terraform-provider-cloudflare/internal/sdkv2provider	38.044s

[github-actions]

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