fix(e2e): use provider identity for managed credential paths

[shiju-nv]

Summary

The credential-driver E2E test calculates managed Kubernetes Secret names and Vault paths using only the provider name and credential key. The credential drivers also include the provider workspace and provider ID, so the test can look for an object the driver never created and report a false failure.

Read the stored provider identity and derive the expected storage paths from the same four values used by the drivers:

• Provider workspace
• Provider ID
• Provider name
• Credential key

This changes only the E2E test. Production credential handling, APIs, policy behavior, and storage formats are unchanged.

Related Issue

Fixes #2983.

Changes

• Read the created provider's ID and workspace from provider list --output json.
• Calculate the managed credential hash from workspace, provider ID, provider name, and credential key.
• Use that hash for both the Kubernetes Secret and Vault path assertions.
• Keep the existing assertions for credential contents and cleanup behavior.

The core correction was extracted from Drew Newberry's signed commit 10dbe53b1 in #1868.

Testing

• mise run pre-commit passes
• Unit tests added/updated (not applicable: this changes an existing E2E test)
• E2E tests added/updated (if applicable)

Checklist

• Follows Conventional Commits.
• Commits are signed off (DCO).
• Architecture docs updated (not applicable: this changes only an E2E test).