Set IAVL config

[facs95]

Description

Bringing changes back from v8.2.3. Setting IAVLFastNode config to false to avoid AppMismatch issues.

Closes: #XXX

---

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

PR review checkboxes:

I have...

• added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• included the correct type prefix in the PR title
• targeted the correct branch (see PR Targeting)
• provided a link in the PR description to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all required CI checks have passed

Code maintenance:

I have...

• written unit and integration tests
• added relevant godoc and code comments.
• updated relevant documentation (docs/) or specification (x/<module>/spec/)

---

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed all author checklist items have been addressed
• confirmed that this PR does not change production code