MoveInitializers splits start state for parsers that do not need this

[oleg-ran-amd]

If MoveInitializers detects that a parser needs a start state split, start also gets split for all the other parsers that follow that first parser in the P4 IR, even if they do not need this.

Parser2 in the code below does not need start split:

parser Parser1() {
  bit<8> l = 0;
  state start {
    transition next;
  }
  state next {
    transition select(l) {
        default: accept;
    }
  }
}

parser Parser2() {
  state start {
    transition  accept;
  }
}

parser proto();
package top(proto p1, proto p2);
top(Parser1(), Parser2()) main;

However, the frontend's output is:

parser Parser1() {
    @name("Parser1.l") bit<8> l_0;
    state start {
        l_0 = 8w0;
        transition start_0;
    }
    state start_0 {
        transition select(l_0) {
            default: accept;
        }
    }
}

parser Parser2() {
    state start {
        transition start_0;
    }
    state start_0 {  <==================
        transition accept;
    }
}

The midend is able to squash start_0 and start for Parser2 above, but there is still no reason to split.