Performance: Enable `fastResultLoading` by default

Created by: umpox

closes: https://github.com/sourcegraph/sourcegraph/issues/6992

Actions before merging this PR:

• Check that there were no issues on S2. This has already been enabled fully on that instance. Slack thread
• Check to see if we can remove the experimental feature entirely, or if this breaks anything. E.g. we have it in our current Sourcegraph.com config here, if we delete the flag will it break something?

Description

This PR:

• Enables enableFastResultLoading by default. This will fetch significantly less KB of data from each search result.

This seems like it should have been enabled a while ago, we just didn't get around to it .

Note This is currently fully enabled on S2 for thorough testing, I don't see any reason why we can't enable this though.

Before

After

Test plan

Tested locally

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.