multitenant: SHOW RANGES leaks adjacent tenant ID

**Only the ID of the next tenant is displayed, not table/index IDs or primary keys.**

In a cluster with multiple tenants, the output of `SHOW RANGES` for one tenant will display the next tenant's ID
```
tc := testCase{
system: tenantExpected{
result: [][]string{
{"", "…/1"},
{"…/1", ""},
},
},
secondaryNoCapability: tenantExpected{
result: [][]string{
{"", "…/104/2/1"},
{"…/104/2/1", ""},
},
},
secondaryCapability: tenantExpected{
result: [][]string{
{"", "…/104/2/1"},
{"…/104/2/1", "` which is tenant 10's span's start key.
`secondaryNoCapability` is tenant 10, but sees this span end key `` which is tenant 10's span's start key.

Jira issue: CRDB-22863

Epic CRDB-26091