Upgrade to go 1.22, unpin envtest and goimports

[AObuchow]

We've had to pin envtest and goimports because we're currently using go 1.20 throughout the repo.

Originally, this was because go 1.22 was not available for the stable release of Fedora. Now, go 1.22 is available in Fedora 40 so we should finally upgrade the go version used throughout the repo.

[AObuchow]

Update: Unfortunately, it turns out we can't upgrade to go 1.22 yet because though it's available on Fedora (I'm running 1.22.5) it's not available yet for the go-toolset image we use in our Dockerfiles. The latest version of go-toolset goes up to go 1.21.11.

Since goimports v0.25.0 & latest envtest require go >= 1.22.0, for now we could at best only update to go 1.21.11. Both of these tools would have to remain pinned :(

[AObuchow]

This issue is now unblocked by #1348!