TDL-6619: Enable leads stream

[savan-chovatiya]

Description of change

TDL-6619: Enable leads stream.

• Enabled leads stream
• Added one condition for returning record with maximum replication_key for writing bookmark as currently, it is breaking tap(parsing None as a date) when no data is available for leads.

NOTE: No data available currently for leads and for that we need to create/activate ads and do some interaction but it's chargeable activity. As per card comment, scope related to 'leads' is already added in the OAuth app and marked ready to use so we will comment integration tests to not consider 'leads' stream in sync-related tests for now as per discussion.

Manual QA steps

Risks

Rollback steps

• revert this branch