Improve AVM module completion readability (long paths + small suggest widget)

When authoring Bicep modules from the public registry (AVM), the completion dropdown is too narrow for the long module paths. Most AVM paths share long prefixes (e.g., `avm/ptn/...`) and differ toward the end, so it's hard to visually scan the list. The problem gets worse at higher editor zoom levels.

### Steps to Reproduce

- Open a Bicep file.
- Type: `module test 'br/public:` and trigger completions.
- Browse the AVM module list.
- Increase editor zoom (e.g., 120% or 150%) and repeat.

The suggest widget is narrow; long items truncate. The distinguishing part of the module path is hard to see, especially at higher zoom.

### Expected Result

Completion list remains readable even with long module paths. Users can quickly identify items by their unique suffix (module name).

**Describe the solution you'd like**

- Suffix-first labels: show the tail segment as the main label, with the prefix in a dimmed description.
- Prefix de-emphasis using `labelDetails.description`.
- Keep full path as `insertText` while displaying a shorter label.
- Smarter sort/filter to prioritize suffix matches.