This teaches the program how to collect information from multiple
Go versions and join it together. For this to work, it needs to
select the Go versions itself, which is now possible via GOTOOLCHAIN.
The merging of data is fairly simple; we join the results from all
versions, and we remove duplicates from older Go versions.
Start producing output with the Go version noted on every data point,
so that we can easily scan what each Go version is contributing.
Daniel Martí