Support `UseCachedPackages` flag to prioritize existing local files during installation

### **Description**

Currently, when a module is uninstalled via IPM, the physical source files often remain in the installation directory (e.g., `/ipm///`). However, if a user attempts to `install` that same module/version again, IPM ignores the existing local files and initiates a fresh download from the remote registry.

### **Proposed Solution**

I propose a new configuration setting that allows IPM to detect and use existing local source files instead of redownloading them.

**Name:** `UseCachedPackages`

**Logic:**
When running `zpm "install "`:

1. **Check Setting:** If `UseCachedPackages` is set to `1`.
2. **Local Scan:** IPM checks if the directory `/ipm///` exists and contains a valid `module.xml`.
3. **Action:**
* **If Local Files Exist:** IPM skips download from registry and proceeds directly to loading/compiling the existing local files (similar to a `load` command).
* **If Local Files Do Not Exist:** IPM performs the standard download from the registry.

### **Requested Flag Behavior:**

* **`0` (Default):** Maintain current behavior (always fetch from registry).
* **`1`:** Prefer local files if they exist in the standard IPM directory.