make it possible to specify the Go version

My quic-go build recently started failing, since I updated quic-go to require Go 1.20 (https://github.com/quic-go/quic-go/pull/3936).

It looks like oss-fuzz currently still uses Go 1.19 (released in August 2022, almost one year ago): https://github.com/google/oss-fuzz/blob/cd48a6e2415fc52bf8d8cc155ed61f4b7711e160/infra/base-images/base-builder/install_go.sh#L21

It would be nice if oss-fuzz would use the most recent Go version, as most projects quickly update their compiler (updating the Go version is usually pretty frictionless due to Go's backwards-compatibility guarantee).

An even better resolution of this issue would be to include multiple Go version in the base image. go would then reference the most recent Go version, and other Go versions could (for example) be symlinked / aliased as go1.19 etc. This would be relevant projects that use version-dependent code paths (as quic-go does for its crypto/tls fork still needed for Go 1.20, but obsolete in Go 1.21).

Start by reading infra/base-images/base-builder/install_go.sh, especially the currently pinned Go 1.19 installation. Determine how version selection or multiple installed versions should be exposed, then verify that the base image supports the Go-version-dependent use case described for quic-go and older Go versions.