Add transcoder for Unjail Validator txn type. Add approve UI support for this new txn type.

[lazynina]

[!WARNING] This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite. Learn more

• #297
• #296 👈
• #295
• #294
• #293
• #292
• #291
• #290 : 2 other dependent PRs (#298 , #301 )
• main

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