Docs for SERVER-35293: Add counts of active and inactive transactions to serverStatus

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Original Description

Description:

serverStatus additions.

Engineering Ticket Description:

We want to output the number of active and inactive transactions in the "transactions" serverStatus section by utilizing the existing metrics tracked in the currentActive and currentInactive fields of MultiDocumentTransactionStats. If they do not already exist, we need to add currentActive and currentInactive fields to the transactions_stats.idl class, so that we can serialize these counters to the serverStatus output object in the TransactionsSSS::generateSection method. We also need to make sure that the ServerTransactionsMetrics::updateStats updates the appropriate fields on the TransactionsStats object.

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Description

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