x/gamm: Make all internal set functions private (backport #2013)

[mergify]

This is an automatic backport of pull request #2013 done by Mergify.
Cherry-pick of 7fb5f82 has failed:

On branch mergify/bp/v10.x/pr-2013
Your branch is up to date with 'origin/v10.x'.

You are currently cherry-picking commit 7fb5f824.
  (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:   app/apptesting/test_suite.go
	modified:   app/upgrades/v9/prop214.go
	modified:   app/upgrades/v9/prop214_test.go
	new file:   x/gamm/keeper/export_test.go
	modified:   x/gamm/keeper/params.go
	modified:   x/gamm/keeper/pool.go
	modified:   x/gamm/keeper/pool_service.go
	modified:   x/gamm/keeper/share.go
	modified:   x/gamm/keeper/swap.go
	modified:   x/gamm/keeper/total_liquidity.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md
	both modified:   app/upgrades/v4/upgrade_test.go
	both modified:   app/upgrades/v4/upgrades.go
	both modified:   x/gamm/genesis.go

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

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[github-actions]

This pull request has been automatically marked as stale because it has not had any recent activity. It will be closed if no further activity occurs. Thank you!

[p0mvn]

Closing since, we would have to be backporting to v11.x instead