Example setup for tooling

[mockersf]

Objective

• Meshlet continuous LOD #12755 introduced the need to download a file to run an example
• This means the example fails to run in CI without downloading that file

Solution

• Add a new metadata to examples "setup" that provides setup instructions
• Replace the URL in the meshlet example to one that can actually be downloaded
• example-showcase execute the setup before running an example

[BD103]

What's the reason for storing the meshlet in a separate repository in the first place? (cc @JMS55)

Edit:

It looks like the file may get updated frequently. Sounds good 👍

[JMS55]

This could use some helper functions to simplify the nesting/amount of maps and casts and such, but otherwise lgtm.