sql: investigate why TestPGTest/large_input does not work with a shared process virtual cluster

[herkolategan]

Describe the problem

When running TestPGTest with a shared process virtual cluster, the large_input subtest fails.

How to reproduce

Set the following in TestServerArgs to force a shared process tenant and cause the failure to happen.

DefaultTestTenant: base.SharedTestTenantAlwaysEnabled,

Expected behavior
The test should pass when running with a shared process virtual cluster, unless after investigation the test is expected not to work with one.

• Probably TestDistSQLReceiverDrainsMeta has a related failure, so that test is also tracked by this issue.

Ref: #112857
Epic CRDB-48944
Jira issue: CRDB-32696