Bump app version after upgrade in v2 path

[julienrbrt]

ref: #16455, #21176

Baseapp implements the version modifier:
https://github.com/cosmos/cosmos-sdk/blob/3e41324/core/app/app.go#L70-L77

x/upgrade updates that version modifier in

cosmos-sdk/x/upgrade/keeper/keeper.go

Line 437 in 19e0de5

if k.versionModifier != nil {

, which is then returned in abci_info.

On server/v2 we get them from x/consensus params:

cosmos-sdk/server/v2/cometbft/abci.go

Line 167 in 19e0de5

appVersion = cp.Version.GetApp()

but don't upgrade them in x/upgrade

Proposal

• Update app version in baseapp (done) and server/v2
• Remove VersionModifier from core/server as it is baseapp specific
• Or make the version update consistent between baseapp & server/v2 to not have two different handling in x/upgrade

Requirements: Do not introduce a x/consensus dependency in x/upgrade (as this module is cometbft specific).