console: don't exit on ctrl-c, only on ctrl-d (#21660)

* add interrupt counter

* remove interrupt counter, allow ctrl-C to clear ONLY, ctrl-D will terminate console, stop node

* format

* add instructions to exit

* fix tests

cmd/geth/consolecmd_test.go

@@ -66,6 +66,7 @@ at block: 0 ({{niltime}})
  datadir: {{.Datadir}}
  modules: {{apis}}
 
+To exit, press ctrl-d
 > {{.InputLine "exit"}}
 `)
 	geth.ExpectExit()
@@ -159,6 +160,7 @@ at block: 0 ({{niltime}}){{if ipc}}
  datadir: {{datadir}}{{end}}
  modules: {{apis}}
 
+To exit, press ctrl-d
 > {{.InputLine "exit" }}
 `)
 	attach.ExpectExit()