Add `waza` to the file prefixes to allow waza specific editing tools

[aeschli]

The generated file eval.yaml and tasks/*.yaml are very generic. It would be nicer if the file names where waza specific, e.g, waza-eval.yaml and tasks/*.waza-task.yaml.

The current file names collide with similarly named files from other tools.

More specific, unique files name would allow it associate thee files with waza specific tooling in VS Code.
A first and simple would be to associate them with their schemas

    ],
    "yamlValidation": [
      {
        "fileMatch": "waza-eval.yaml",
        "url": "https://raw.githubusercontent.com/microsoft/waza/refs/heads/main/schemas/eval.schema.json"
      }
    ]

BTW an alternative is to add a schema comment to each of these files

# yaml-language-server: $schema=https://raw.githubusercontent.com/microsoft/waza/refs/heads/main/schemas/eval.schema.json
name: accessibility-eval
description: Auto-generated eval for accessibility.
skill: accessibility
version: "1.0"
config:
 ...