feat: add parameter list parsing and up to 8 function call primitives

Extract shared parameter list parsing from namedSignature into a new parameterList function called by function, and replace single fn_call primitive with fn_call0 through fn_call8 primitives to support up to 8 arguments. Add comprehensive fn_parameters.wren test covering 0-8 parameter calls.

test/fn_call.wren

@@ -1,3 +0,0 @@
-io.write((fn 123).call) // expect: 123
-
-// TODO(bob): Arguments.

test/fn_parameters.wren

@@ -0,0 +1,26 @@
+var f0 = fn 0
+io.write(f0.call) // expect: 0
+
+var f1 = fn(a) a
+io.write(f1.call(1)) // expect: 1
+
+var f2 = fn(a, b) a + b
+io.write(f2.call(1, 2)) // expect: 3
+
+var f3 = fn(a, b, c) a + b + c
+io.write(f3.call(1, 2, 3)) // expect: 6
+
+var f4 = fn(a, b, c, d) a + b + c + d
+io.write(f4.call(1, 2, 3, 4)) // expect: 10
+
+var f5 = fn(a, b, c, d, e) a + b + c + d + e
+io.write(f5.call(1, 2, 3, 4, 5)) // expect: 15
+
+var f6 = fn(a, b, c, d, e, f) a + b + c + d + e + f
+io.write(f6.call(1, 2, 3, 4, 5, 6)) // expect: 21
+
+var f7 = fn(a, b, c, d, e, f, g) a + b + c + d + e + f + g
+io.write(f7.call(1, 2, 3, 4, 5, 6, 7)) // expect: 28
+
+var f8 = fn(a, b, c, d, e, f, g, h) a + b + c + d + e + f + g + h
+io.write(f8.call(1, 2, 3, 4, 5, 6, 7, 8)) // expect: 36