Upgrade the minimum supported Go version to fix security alerts

[dxsup]

There are two dependabot alerts #4 #5 that can't raise PRs automatically because they need to upgrade the go packages. But the packages are dependencies of github.com/mdlayher/netlink.

github.com/Kindling-project/kindling/collector/pkg/metadata/conntracker/internal imports
        github.com/mdlayher/netlink imports
        github.com/mdlayher/socket imports
        golang.org/x/sync/errgroup loaded from golang.org/x/sync@v0.0.0-20210220032951-036812b2e83c,
        but go 1.16 would select v0.0.0-20220722155255-886fb9371eb4

To fix these alerts, we have to upgrade the Go version to at least 1.18 since the version of github.com/mdlayher/netlink we need requests Go 1.18+.

There are several components that we need to upgrade:

• The minimum version specified in go.mod.
• The Go version pre-installed in the builder image.

[dxsup]

Closed via #463