serverutils: specify cluster settings and capabilities for default test tenant

Currently tests that run probabilistically with a test tenant have some cluster settings and capabilities enabled by default.

For example the following cluster settings are applied on start-up.
```
[]settings.Setting{
sql.SecondaryTenantScatterEnabled,
sql.SecondaryTenantSplitAtEnabled,
sql.SecondaryTenantZoneConfigsEnabled,
sql.SecondaryTenantsMultiRegionAbstractionsEnabled,
}
```

Furthermore we also conditionally grant capabilities to the default test tenant:
```
ALTER TENANT [$1] GRANT CAPABILITY can_use_nodelocal_storage=true
```

Some tests however might require additional capabilities or cluster settings specifically when the test tenant is running.
One such example are tests that need to be able to debug the process: `TestAdminDebugPprof`.

This issue aims to address that requirement for a test to be able to specify which capabilities and cluster settings it would like to be set when a test tenant is running.

Jira issue: CRDB-32792

Epic CRDB-38970