kv/kvnemesis: enable DRPC for tests

The `pkg/kv/kvnemesis` package currently has DRPC explicitly disabled in its `TestMain`:

```go
serverutils.InitTestServerFactory(server.TestServerFactory,
serverutils.WithDRPCOption(base.TestDRPCDisabled),
serverutils.WithTenantOption(base.TestIsSpecificToStorageLayerAndNeedsASystemTenant))
```

This package should be enabled to run with DRPC to ensure coverage of the DRPC code path under kvnemesis's randomized KV workloads.

**Work involved:**
- Change `base.TestDRPCDisabled` to `base.TestDRPCEnabledRandomly` in `pkg/kv/kvnemesis/main_test.go`
- Run tests and investigate any failures under DRPC
- Disable DRPC for individual failing tests if needed while root-causing

Epic: none

Jira issue: CRDB-63821