DLPXECO-13068 Allow silent migration of toolkit_path for environments created before v4.0.0

[gmanhas23]

Problem

When upgrading Terraform provider from v3.3.2 to v4.1.0, users encounter a "cannot update options [toolkit_path]" error. This happens because toolkit_path moved from being a top-level parameter to a nested parameter within the hosts block, but the provider doesn't handle this migration gracefully.

Solution

This PR implements a silent migration strategy for the toolkit_path parameter:

1. Added toolkit_path as updatable: Added to updatableEnvKeys map to allow updates
2. Made updates non-destructive: Added to isDestructiveEnvUpdate as false to prevent VDB/dSource downtime
3. Silent migration: Added DiffSuppressFunc to suppress diff when toolkit_path is set to null/empty, allowing seamless transition from top-level to nested structure
4. Backward compatibility: Maintains support for existing v3.3.2 configurations while enabling v4.1.0 features

Changes Made

• internal/provider/commons.go: Added toolkit_path to updatable and non-destructive maps
• internal/provider/resource_environment.go: Added DiffSuppressFunc for silent parameter migration

Testing

• ✅ Validated with v3.3.2 → v4.1.0-fix upgrade scenario
• ✅ Confirmed terraform plan shows "No changes" (silent migration)
• ✅ Verified backward compatibility with existing environments
• ✅ Tested update-in-place functionality works without errors

Impact

• Users: Seamless upgrade path from v3.3.2 to v4.1.0+ without breaking changes
• Operations: No VDB/dSource downtime during provider upgrades
• Support: Reduces upgrade-related support tickets and issues

Fixes: DLPXECO-13068

[Uddipaan-Hazarika]

LGTM