Add namespace bundle count support

[freeznet]

Summary

• add an optional, computed, ForceNew bundles attribute to pulsar_namespace
• use the broker default when omitted and hydrate the actual count during refresh and import
• create namespaces with initialized policies so Pulsar 4.0.3 receives non-null replication cluster data
• validate the positive Java int range while preserving valid non-power-of-two counts

Validation

• go test ./...
• go vet ./...
• go build ./...
• golangci-lint v2.4.0 run -c .golangci.yaml ./...
• tfproviderlint with the repository lint flags
• Pulsar 4.0.3 acceptance: omitted broker default, explicit 3 bundles, ForceNew replacement from 3 to 6, and import/empty-plan coverage
• go generate ./... and git diff --check

Fixes #231.

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[github-actions]

@freeznet:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)