Export sorted map

[demmer]

Description

Manually generate the exported autoload map in sorted order.

Details

At Slack we commit the vendor autoload map to source control, which makes diffs hard to comprehend given that the map is unordered.

This change replaces the var_export with manually generated code after sorting the arrays so that the generated autoload map should be stable.

CLA

@ssandler requested that I be added to the Slack corporate CLA at some point.