feat: bump up cosmos-sdk v0.50.8, cometbft v0.38.9, ibc-go v8.3.2

[dudong2]

Description

• cosmos-sdk v0.50.6 -> v0.50.8
• cometbft v0.38.6 -> v0.38.9
• ibc-go v8.2.1 -> v8.3.2

I synced ibc/testing, which is used for testing in the onboarding module, with codes from cosmos/ibc-go@v8.3.2 and removed un-necessary files. However, this is a temporary measure and I will eventually move towards removing ibc/testing and utilising ibc-go.

Closes: #XXXX

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[dongsam]

LGTM, seems need to bump ethermint to b-harvest/ethermint#13 after merged

[poorphd]

LGTM