bug(flaky-test): payments credential provider setup

[Hweinstock]

Problem

 [payments-strands-bedrock]:deploy stdout={"success":false,"logPath":"agentcore/.cli/logs/deploy/deploy-20260617-195959.log","error":"Payment setup failed: Credential provider for \"E2ePayConn\": Failed to create payment credential provider \"E2ePayMgr-E2ePayConn-cdp\": Payment API error (400): {\"fieldList\":null,\"message\":\"Credential provider with name: E2ePayMgr-E2ePayConn-cdp already exists\",\"reason\":null}"}

it looks like the credential provider is using a static name, and likely conflicted with the version created by a concurrent execution.

Definition of Done

• verify the created payments credentials have a unique suffix.