refactor(payments): merge credential setup into pre-deploy-identity

Payment credential providers use the same /identities/ endpoint as API key
and OAuth providers. Move setupPaymentCredentialProviders, hasPaymentCredentialProviders,
and cleanupPaymentCredentialProviders into pre-deploy-identity.ts alongside
the other credential provider operations.

- Delete pre-deploy-payments.ts (merged into pre-deploy-identity.ts)
- Delete payment-types.ts (types inlined in pre-deploy-identity.ts)
- Rename: setupPaymentResources → setupPaymentCredentialProviders
- Rename: hasPaymentManagers → hasPaymentCredentialProviders
- Update all import paths and barrel exports
- Update test imports

Author: aidandaly24

package-lock.json

@@ -87,12 +87,7 @@
     "@aws-sdk/client-sts": "^3.893.0",
     "@aws-sdk/client-xray": "^3.1003.0",
     "@aws-sdk/credential-providers": "^3.893.0",
-<<<<<<< HEAD
     "@aws/agent-inspector": "0.4.1",
-=======
-    "@aws/agent-inspector": "0.3.0",
-    "@aws/agentcore-cdk": "file:../agentcore-l3-cdk-constructs",
->>>>>>> 60e516c7 (fix(payments): bugbash findings — 11 bugs fixed)
     "@commander-js/extra-typings": "^14.0.0",
     "@opentelemetry/api": "^1.9.1",
     "@opentelemetry/exporter-metrics-otlp-http": "^0.215.0",