flag: add BoolFunc(name, usage string, fn func(string)error) #53747
Description
Using flag.Func forces you to always pass an argument. Sometimes we don't really need an argument and its really convenient to be able to just call this flags without passing any dummy value.
Example:
Setting the flag --start-server will ask you to specify a value and also mentions it on the usage
-start-server value
Starts the server