Switch to QuickJS for CouchDB JS engine

[garethbowen]

Describe the performance issue

View rebuilding is slow which is a big problem particularly when doing an update which changes a view requiring the whole index to be rebuilt.

Describe the improvement you'd like

CouchDB 3.4.x introduced a new JS engine called QuickJS which promises 4-5x speed improvement and 6x improvement in memory usage. It's off by default. Try turning it on and see if we can get similar gains.

Describe alternatives you've considered

To Reproduce

1. Get a db with a lot of realistic data
2. Back up the db so you can re-run the test easily
3. Change a view (even a whitespace change) to trigger a complete rebuild
4. Measure the time, cpu usage, memory usage, disk usage until completion
5. Restore the backup
6. Change the JS engine to QuickJS (docs)
7. Change the view and measure the time again

Measurements

• Time to complete
• CPU usage average and peak
• Memory usage average and peak
• Disk usage peak

Environment

• Instance: A cloud instance would be ideal, but as long as the specs are the same for both runs it should be ok
• Browser: N/A
• Client platform: N/A
• App: couchdb
• Version: latest

Additional context

Blocked by #9303

[lorerod]

Moved to 4.15.0 so as not to hold up the release.