feat: add Sequence.all method and forall documentation with tests

Implement `all(f)` method on Sequence class that returns true if all elements pass the predicate function. Add corresponding documentation entry for `forall(predicate)` in core-library.markdown. Include three test files covering basic functionality, non-boolean return handling, and non-function argument error cases.

test/list/forall.wren

@@ -0,0 +1,9 @@
+var a = [1, 2, 3]
+var b = a.all {|x| x > 1 }
+IO.print(b) // expect: false
+
+var d = a.all {|x| x > 0 }
+IO.print(d) // expect: true
+
+var e = [].all {|x| false }
+IO.print(e) // expect: true

test/list/forall_non_bool_returning_fn.wren

@@ -0,0 +1 @@
+[1, 2, 3].all {|x| "string" } // expect runtime error: String does not implement method '!' with 0 arguments.

test/list/forall_non_function_arg.wren

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+[1, 2, 3].all("string") // expect runtime error: String does not implement method 'call' with 1 argument.