Add health check type configuration and improve CF API compatibility

[ivanovac]

Summary

This PR enhances the switchblade testing framework with health check configuration support and improves Cloud Foundry API compatibility for buildpack testing scenarios.

Changes

1. Health Check Configuration Support

• Added WithHealthCheckType() method to DeployProcess interface and implementations
  • CF implementation: Calls cf set-health-check to configure process-based or port-based health checks
  • Docker implementation: No-op (Docker doesn't use CF health check types)
• Use case: Enables tests to explicitly specify health check type for apps that don't run web servers
  • WithHealthCheckType("process") - For scripts/background processes that don't serve HTTP
  • Default (no call) - Uses CF's default port-based health check for web servers

2. CF API v2 to v3 Migration

• Updated route retrieval in stage.go from /v2/apps/{guid}/routes to /v3/apps/{guid}/routes
• Fixes compatibility with CF environments where API v2 endpoints are disabled
• Added stderr logging to route fetch operation for better debugging

3. Graceful TCP Route Handling

• Made TCP route creation non-fatal in setup.go
  • Previously: Fatal error when TCP port pool exhausted
  • Now: Logs warning and continues with HTTP routes only
• Rationale: Many buildpack tests only need HTTP routes; TCP is optional for most scenarios
• Preserves shared library compatibility: Other projects using switchblade may need TCP, so functionality remains but doesn't block tests

4. Buildpack Deletion Fix

• Removed -s/--stack flag from cf delete-buildpack command in initialize.go
• Fixes: "stackless buildpack already exists" errors during test initialization
• Approach: Delete buildpack without stack filter first, then recreate with correct configuration

Motivation

These changes were needed to support R buildpack integration tests running on Cloud Foundry environments with:

• CF API v2 endpoints disabled
• Limited TCP port pools
• Apps using process-based health checks (R scripts, background jobs)
• Modern CF deployments requiring v3 API usage

Testing

• ✅ Verified with R buildpack integration tests on CF (cflinuxfs4)
• ✅ CF platforms tested
• ✅ Process health check tests passing
• ✅ TCP route warnings logged but tests continue successfully

Backward Compatibility

• ✅ All changes are backward compatible
• ✅ WithHealthCheckType() is optional (no call = default behavior)
• ✅ Docker platform unchanged (health check is no-op)
• ✅ TCP routes still attempted but failures don't block deployments

[ramonskie]

looks good. but we need to squash this when merging