Disallow non-Num arguments in Num for min(_), max(_), clamp(_,_), pow(_) and atan(_) (#859)

* Disallow non-Num arguments in `Num.min(_)`, `Num.max(_)`, `Num.clamp(_,_)`

Previously this was an Undefined Behavior

* also validate args for pow, atan2, add tests, fix error messages

Co-authored-by: ruby0x1 <ruby0x1@pm.me>

test/core/number/atan2_x_not_num.wren

@@ -0,0 +1 @@
+0.atan(false) // expect runtime error: x value must be a number.

test/core/number/clamp_max_not_num.wren

@@ -0,0 +1 @@
+1.clamp(0, false) // expect runtime error: Max value must be a number.

test/core/number/clamp_min_not_num.wren

@@ -0,0 +1 @@
+1.clamp(false, 2) // expect runtime error: Min value must be a number.

test/core/number/max_other_not_num.wren

@@ -0,0 +1 @@
+1.max(false) // expect runtime error: Other value must be a number.

test/core/number/min_other_not_num.wren

@@ -0,0 +1 @@
+1.min(false) // expect runtime error: Other value must be a number.

test/core/number/pow_power_not_num.wren

@@ -0,0 +1,2 @@
+1.pow(false) // expect runtime error: Power value must be a number.
+