feat: remove all import placeholders using the xast pkg (backport #4004)

[mergify]

Description

• Remove all ignite placeholder into the .plush imports and add them using the xast.AppendImports function;
• Remove the keeper definition placeholder into the app.go.plush and add them using the xast.ModifyFunction function;
• Remove unused placeholders;

  ---

  This is an automatic backport of pull request feat: remove all import placeholders using the xast pkg #4004 done by Mergify.

[mergify]

Cherry-pick of 59400a5 has failed:

On branch mergify/bp/release/v28.x.y/pr-4004
Your branch is up to date with 'origin/release/v28.x.y'.

You are currently cherry-picking commit 59400a52.
  (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:   changelog.md
	modified:   ignite/pkg/cosmosanalysis/app/testdata/modules/app_config/app_config.go
	modified:   ignite/pkg/cosmosanalysis/app/testdata/modules/spn/app.go
	modified:   ignite/pkg/cosmosanalysis/module/testdata/earth/app/app_config.go
	modified:   ignite/templates/app/files-minimal/app/app.go.plush
	modified:   ignite/templates/app/files-minimal/app/app_config.go.plush
	modified:   ignite/templates/app/files/app/app.go.plush
	modified:   ignite/templates/app/files/app/app_config.go.plush
	modified:   ignite/templates/app/files/app/ibc.go.plush
	modified:   ignite/templates/message/placeholders.go
	modified:   ignite/templates/module/create/base.go
	modified:   ignite/templates/module/create/files/base/x/{{moduleName}}/types/genesis.go.plush
	modified:   ignite/templates/module/create/ibc.go
	modified:   ignite/templates/module/placeholders.go
	modified:   ignite/templates/typed/genesis.go
	modified:   ignite/templates/typed/list/genesis.go
	modified:   ignite/templates/typed/map/map.go
	modified:   ignite/templates/typed/placeholders.go
	modified:   ignite/templates/typed/singleton/singleton.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   ignite/templates/ibc/placeholders.go

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

[julienrbrt]

We shouldn't backport this. A chain scaffolded with v28 will still have the placeholders. I think it is more a v29 change