v1.18: extends Turbine fanout experiment to wider fanout values (backport of #2373)

[mergify]

Problem

Based on previous Turbine fanout experiment, larger fanouts are more effective in propagating shreds and reducing repairs: https://discord.com/channels/428295358100013066/478692221441409024/1265782094211321897

However the optimal fanout value cannot be inferred from the experiment.

Summary of Changes

In order to identify optimal fanout value, this commit extends the experiment with wider fanout values.

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This is an automatic backport of pull request #2373 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 57144b0 has failed:

On branch mergify/bp/v1.18/pr-2373
Your branch is up to date with 'origin/v1.18'.

You are currently cherry-picking commit 57144b0cea.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   turbine/src/cluster_nodes.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   sdk/src/feature_set.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[behzadnouri]

This is a slight and trivial modification of the experiment currently running on mainnet.
Ideally I would like to get this out asap so that we can settle the optimal turbine fanout before things get more complicated and harder to interpret (e.g. multiple clients, etc).

[bw-solana]

LGTM