cli/demo,cdc: enable rangefeeds by default

[HonoreDB]

Fixes #82719,
which made it annoying to run changefeeds in cockroach demo
as you need to enable rangefeeds twice, once at the system
level. Now cockroach demo enables rangefeeds at startup.

You can override this behavior for performance or to demo
the process of enabling rangefeeds with the flag
--auto-enable-rangefeeds=false.

Release note (cli change): cockroach demo now enables rangefeeds by default. You can restore the old behavior with --auto-enable-rangefeeds=false.

[cockroach-teamcity]

This change is 

[knz]

Curious: what's the benefit of enabling the user to disable the feature?

Reviewed 7 of 8 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @amruss)

[HonoreDB]

Curious: what's the benefit of enabling the user to disable the feature?

I feel like I've seen (or done) a changefeed demo at least once where the user hits the "you need this cluster setting" error deliberately, talks through the implications, and then demonstrates setting it to true. Also if you're doing something performance-sensitive with a workload it could be annoying to have to turn it off via sql.

[HonoreDB]

Thanks for the reviews!

[HonoreDB]

bors r=[knz,stevendanna]

[craig]

Build succeeded:

• GitHub CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from b0d2e6d to blathers/backport-release-22.1-83282: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.1.x failed. See errors above.

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