fix: call AfterUnbondingInitiated for new unbonding entries only

[MSalopek]

Description

Closes: #16042

An earlier change in #12967 introduced behaviour that causes the AfterUnbondingInitiated staking hook to be called with an invalid unbondingId in SetUnbondingDelegationEntry. The issue affects unbonding operations, redelegation behaviour does not seem to be affected. The issue can cause interchain-security provider chains to panic.

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[julienrbrt]

Can we get a changelog + a test here?

[MSalopek]

Can we get a changelog + a test here?

Yes. I'll add the tests and the changelog 👍

[faddat]

Currently working on:

• Upgrade to sdk 47 interchain-security#869

Just curious if this will be able to be backported to 47, or if we need to begin to target main. Thanks.

[MSalopek]

@julienrbrt Tests and changelog entries were added.
Please let me know if you want to do something differently.

[julienrbrt]

Thanks, could you fix the linting issues?

[MSalopek]

Thanks, could you fix the linting issues?

Fixed!

[julienrbrt]

lgtm! However, I do not think we can backport that to v0.47 🤔

[julienrbrt]

Reminder for myself, precise a behavior change in the UPGRADING.md and/or changelog.