Renames file to be clearer it is a generated file

- LZ compresses emoji data

Avoids unneeded build re-triggering while watching

This is because the marketplace doesn't know about pre-releases and our versioning model makes the latest pre-release always the latest version (which is what shows on the marketplace)

Since pre-releases feed the marketplace content

Until the VS Code marketplace can truly handle pre-releases we can't adopt the current limited pre-release provided by VS Code

Deprecates Insiders extension