[Feature]: Add compiler assertions to UPGRADING doc for v0.50

[colin-axner]

Summary

Add a list of recommended compiler assertions developers should add into their module.

Problem Definition

The API for several functions such as BeginBlock, EndBlock, InitGenesis and ExportGenesis has changed and most of theses functions are now optional removing compiler safety by default, but developers can reference the new Has interfaces to ensure their function implements the expected interface correctly.

Proposed Feature

Add a list of Has interface compiler assertions developers can copy over as necessary, such as:

var (
	_ module.AppModule           = (*AppModule)(nil)
	_ module.AppModuleBasic      = (*AppModuleBasic)(nil)
	_ module.AppModuleSimulation = (*AppModule)(nil)
	_ module.HasGenesis          = (*AppModule)(nil)
	_ appmodule.AppModule        = (*AppModule)(nil)
	_ appmodule.HasBeginBlocker  = (*AppModule)(nil)
)

you may include only the new interfaces if you like

ref: cosmos/ibc-go#4647, cosmos/ibc-go#4557, cosmos/ibc-go#4563, cosmos/ibc-go#4466