Investigate the remaining issues with pipeline schema from BB

Hello team @atlassian/axon!

I'm resolving some BB issues and decided to move this one here

We might want to investigate if it would be possible to:
1. Point the `bitbucket-pipelines.yaml` schema to the web instead of distributing a copy
2. Not nuke the settings on extension reinstall? (if that still happens)

This issue is prompted by 2 related issues from our old BB repo:
* [Settings getting reset on extension reinstall](https://bitbucket.org/atlassianlabs/atlascode/issues/548/vscode-extension-periodically-erases)
* [Use official BB schema](https://bitbucket.org/atlassianlabs/atlascode/issues/5416/use-official-pipelines-json-schema-for) from @detouched

Edit - more related BB issues:
* [Configuration to stop updating global settings.json's "yaml.schemas"](https://bitbucket.org/atlassianlabs/atlascode/issues/5357/configuration-to-stop-updating-global)

Start by reviewing the three linked Bitbucket issues and the extension's handling of bitbucket-pipelines.yaml schemas and VS Code settings. Determine whether the schema can be referenced from the web and whether reinstalling the extension still resets yaml.schemas; done means documenting findings and implementing or clearly scoping both fixes.

Written by the indexing model from the issue text.