Ensure full commit timing out on replication of large database

[NOTE]: # ( ^^ Provide a general summary of the issue in the title above. ^^ )

## Description
I am trying to replicate the npm registry through couchdb. However, I keep getting the following errors:

{"error":"checkpoint_commit_failure","reason":"Failure on source commit: {'EXIT',{http_request_failed,\"POST\",\n \"https://skimdb.npmjs.com/registry/_ensure_full_commit\",\n {error,{error,req_timedout}}}}"}

[NOTE]: # ( Describe the problem you're encountering. )
[TIP]: # ( Do NOT give us access or passwords to your actual CouchDB! )

## Steps to Reproduce

I am using version 3.3.2. When post a request to the _ensure_full_commit endpoint, it returns something that looks like this:

{"ok":true,"instance_start_time":"1686442464"}

However, based on the documentation, it should be returning an instance start time of 0.

[NOTE]: # ( Include commands to reproduce, if possible. curl is preferred. )

## Expected Behaviour

[NOTE]: # ( Tell us what you expected to happen. )

## Your Environment

[TIP]: # ( Include as many relevant details about your environment as possible. )
[TIP]: # ( You can paste the output of curl http://YOUR-COUCHDB:5984/ here. )

{"couchdb":"Welcome","version":"3.3.2","git_sha":"11a234070","uuid":"358bddb8b0671d6dc8774db0a626edef","features":["access-ready","partitioned","pluggable-storage-engines","reshard","scheduler"],"vendor":{"name":"The Apache Software Foundation"}}

* CouchDB version used:
* Browser name and version:
* Operating system and version:

## Additional Context

[TIP]: # ( Add any other context about the problem here. )

Start by reproducing the replication failure against the _ensure_full_commit endpoint on CouchDB 3.3.2 and compare its response with the documented instance start time. Trace the checkpoint commit timeout and determine what behavior should be considered correct; done means large-database replication no longer times out and the endpoint response matches the documentation.

Written by the indexing model from the issue text.