test: update block proposer in testing (backport #7430)

Description

Currently, test chains carry the same block proposer for every block. This can lead to a situation where the block proposer isn't part of the validator set, such as after being jailed. This can cause the validation of validator sets to fail in CometBFT v0.38.12, see ValidateBasic.

This PR addresses the issue by incrementing the validator proposer priority in test chains, ensuring that the block proposer is updated in line with changes to the validator set.

closes: #XXXX

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[ ] 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.
This is an automatic backport of pull request #7430 done by Mergify.

cosmos / ibc-go

test: update block proposer in testing (backport #7430) #7454

Description

Quality Gate passed for 'ibc-go'