[xCluster] Ensure sequences_data streams are taken into account for xCluster safe time

[mdbridge]

Jira Link: DB-12923

Description

We are adding sequences_data streams to the set of replicated streams;
we need to make sure the replication progress is taken into account when
computing the xCluster safe time for those databases.

For example, if the sequences_datastream for a database is lagging than
the overall database xCluster safe time should be being held back.

Issue Type

kind/new-feature

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