feat: allow scaling of trusting period for client upgrades

[damiannolan]

Description

Drafting this PR. I can add a finer grained test but stepping through when reducing unbonding period from 21 days to 14 where trusting period is 14, results in a new unbonding period of 14 days and trusting period of 9.33 days

closes: #8184

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against the correct branch (see CONTRIBUTING.md).
• Linked to GitHub issue with discussion and accepted design, OR link to spec that describes this work.
• Code follows the module structure standards and Go style guide.
• Wrote unit and integration tests.
• Updated relevant documentation (docs/).
• Added relevant godoc comments.
• Provide a conventional commit message to follow the repository standards.
• Include a descriptive changelog entry when appropriate. This may be left to the discretion of the PR reviewers. (e.g. chores should be omitted from changelog)
• Re-reviewed Files changed in the GitHub PR explorer.
• Review SonarCloud Report in the comment section below once CI passes.

[damiannolan]

Lemme know if you want a dedicated test func to perform assertions on new trusting period.
This test case covers the code but doesn't do strict assertions.