Migrate PolicyGroup to infer

[iwahbe]

Summary

• Migrates the PolicyGroup resource to the infer framework, replacing
  the legacy gRPC PulumiServicePolicyGroupResource implementation.
• Removes the manual PolicyGroup, PolicyGroupStackReference,
  PolicyGroupPolicyPackReference, and PolicyGroupPolicyPackReferenceInput
  schema blocks from manual-schema.json; infer regenerates them from the
  Go struct definitions.
• Preserves the legacy resource semantics: order-independent diff on
  stacks/accounts/policyPacks, child-account skip-on-remove when the parent
  is still in the input set, version-strip in Check so legacy programs
  that still set the server-derived field upgrade cleanly, and
  replaceOnChanges for name / organizationName / entityType / mode.
• Update sends each batch op in its own request to dodge the Cloud's
  reorder/upsert-by-name behavior, and recovers the real state for the
  checkpoint if a mid-batch op fails; policy-pack equality compares config,
  treating a nil and an empty config map as equal.

Notes

• The generated SDK type for the policy pack's version field changes from
  number to integer, matching the API client's int field. This is a
  minor SDK-shape change but more accurate.
• Existing tests for diff order-independence, policy-pack equality (including
  config), the parent-account child-skip rule, and the version-strip
  behavior cover the new resource shape.

Test plan

• make provider
• make build_sdks
• go test ./... in provider/pkg
• make lint (provider + sdk + examples)
• CI integration tests

[github-actions]

Does the PR have any schema changes?

Found 1 breaking change:

Types

• 🟡 "pulumiservice:index:PolicyGroupPolicyPackReference": properties: "version" type changed from "number" to "integer"
  No new resources/functions.

Maintainer note: consult the runbook for dealing with any breaking changes.

[codecov]

Codecov Report

❌ Patch coverage is 48.33333% with 186 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.59%. Comparing base (6bafee8) to head (33cec2c).

Files with missing lines	Patch %	Lines
provider/pkg/resources/policy_group.go	48.18%	176 Missing and 10 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #837      +/-   ##
==========================================
- Coverage   52.18%   50.59%   -1.59%     
==========================================
  Files          82       82              
  Lines        9598     9514      -84     
==========================================
- Hits         5009     4814     -195     
- Misses       4117     4240     +123     
+ Partials      472      460      -12     

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[iwahbe]

Metabase shows that an __inputs migration isn't necessary.