Prior to this patch, the RPC authz code was restricting
requests from secondary tenants to the range

   /Tenant/ID ... /Tenant/ID/PrefixEnd

However, meanwhile, ever since cockroachdb#104974 was merged,
the tenant keyspace is actually defined as the range

   /Tenant/ID ... /Tenant/<ID+1>

Under the hood, ".PrefixEnd()" computes the "prefix end" key by
incrementing the last byte. Therefore, for most integer values of ID,
/Tenant/ID/PrefixEnd and /Tenant/<ID+1> are equivalent. So the
mismatch above goes unnoticed until ... we run into an ID value for
which they are not equivalent.

An example such value is ID 511. This ID encodes to a sequence of
bytes such that the .PrefixEnd() key is larger than the /Tenant/511
prefix, but strictly smaller than /Tenant/512, which is the actual
exclusive end key for that virtual cluster.

Because of this mismatch, the RPC code would reject any request
from tenant 511 where the end key was /Tenant/512, even though it
should have accepted them.

This patch fixes it.

Release note: None

Prior to this patch, the streaming code was using `.PrefixEnd()` to
compute the exclusive end key of a tenant's keyspace.

As established earlier, this is incorrect, the actual end key is
`/Tenant/<ID+1>`. When the tenant ID is 109, 511 or other values for
which the value encoding needs escape bytes, `.PrefixEnd()` compares
smaller than the keyspace end key.

(We are not currently putting any data in the range
/Tenant/ID/PrefixEnd ... /Tenant/<ID+1> so this did not actually
result in a replication bug. There is no release note needed.)

Release note: None

Prior to this patch, TenantRanges was incorrectly scanning up to
tenantPrefix.PrefixEnd() to collect range descriptors.
Since the actual end key may be different, this resulted
in the endpoint potentially missing out on the last range
of a tenant keyspace, between /Tenant/ID/PrefixEnd and
/Tenant/<ID+1>.

Thankfully, as of this writing no data is ever written in this part of
the keyspace so this bug was not visible in practice.

Release note: None

Prior to this patch, the GC logic was incorrectly scanning up to
tenantPrefix.PrefixEnd() to delete tenant data.

Since the actual end key may be different, this resulted in GC
potentially failing to delete the last portion of a tenant keyspace,
between /Tenant/ID/PrefixEnd and /Tenant/<ID+1>.

Thankfully, as of this writing no data is ever written in this part of
the keyspace so this bug was not visible in practice.

Release note: None

These are the last few mistaken uses of .PrefixEnd().

Release note: None