Small changes to be applied before V1 release

[mpoke]

This issue keeps track of a list of relatively small changes that need to be applied to the code:

• Remove EmitEvent from CCV code, e.g.,

  interchain-security/x/ccv/child/module.go

  Line 337 in eccbfaa

  ctx.EventManager().EmitEvent(

• Check counterparty port id during the channel handshake, i.e.,

  interchain-security/x/ccv/parent/module.go

  Line 236 in eccbfaa

  func (am AppModule) OnChanOpenTry(

  and

  interchain-security/x/ccv/child/module.go

  Line 221 in eccbfaa

  func (am AppModule) OnChanOpenInit(

• Remove hardcoded constants. For example: https://github.com/cosmos/interchain-security/blob/main/x/ccv/types/utils.go#L6

• Implement one consistent scheme for key prefixes. Iota is probably best (see Variable length string prefixes could lead to injection attack #18)

• Correct this bug and increment the ID in the proper place https://github.com/cosmos/interchain-security/blob/main/x/ccv/parent/keeper/relay.go#L113

• Delete the child genesis once the CCV channel for the chainID is OPEN since we no longer need to store it on parent chain.

• keeper.go and other large files could be broken up

[mpoke]

Close as the tasks here were split in different issues: #279, #280, #281, #282