95460: roachtest: run cluster backup schedule by default on gce roachtests r=renatolabs,srosenberg a=msbutler

This patch creates a cluster backup schedule by default on roachtests running on gce. A roachtest writer can override this default behavior by passing option.DefaultStartOptsNoBackups() at cluster.Start().

Roachtests are supposed to mirror a customer env. Like a customer's cluster, roachtests currently run background jobs like gc, sql stats computation, rebalancing etc. But unlike most customer clusters, roachtests do not run scheduled backup jobs by default. Any workload on a roachtest should run just as well with or without with background jobs, but we currently do not test this, at least wrt to scheduled backups. This patch addresses this lack of test coverage.

Fixes #86045

Release note: None

96653: roachprod: replace io/ioutil with os r=rickystewart,srosenberg a=smg260

Epic: none
Fixes: #92862
Release note: None

Co-authored-by: Michael Butler <butler@cockroachlabs.com>
Co-authored-by: Miral Gadani <miral@cockroachlabs.com>