Fix allocated public inputs indexes (#1)

* fix: manage already allocated public inputs with a custom mapping

* fix: initialize CircomCircuit with empty allocated public input variables

* feat: add ability to choose to allocate inputs as witnesses or instances

* chore: remove outdated comment

* test: add relevant tests and asserts for generate_constraints

* chore: add files used for tests

* chore: replace assert_eq with match statement

test-vectors/mycircuit2.circom

@@ -0,0 +1,15 @@
+template Multiplier() {
+    signal input a; // 3
+    signal input b; // 3
+    signal input c; // 3
+    signal temp;
+    signal output d; // 27
+    signal output e; // 9
+
+    temp <== a*b;
+    d <== temp*c;
+    e <== b*c;
+}
+
+component main{public [a, b]} = Multiplier();
+

test-vectors/mycircuit2.sym

@@ -0,0 +1,6 @@
+1,1,0,main.d
+2,2,0,main.e
+3,3,0,main.a
+4,4,0,main.b
+5,5,0,main.c
+6,6,0,main.temp

test-vectors/mycircuit2_constraints.json

@@ -0,0 +1,7 @@
+{
+"constraints": [
+[{"3":"21888242871839275222246405745257275088548364400416034343698204186575808495616"},{"4":"1"},{"6":"21888242871839275222246405745257275088548364400416034343698204186575808495616"}],
+[{"6":"21888242871839275222246405745257275088548364400416034343698204186575808495616"},{"5":"1"},{"1":"21888242871839275222246405745257275088548364400416034343698204186575808495616"}],
+[{"4":"21888242871839275222246405745257275088548364400416034343698204186575808495616"},{"5":"1"},{"2":"21888242871839275222246405745257275088548364400416034343698204186575808495616"}]
+]
+}