feat: replace new keyword with this constructor syntax and ClassName.new() calls across core library and docs

Replace all uses of the `new` reserved word with explicit `this new()` constructor definitions and `ClassName.new()` instantiation calls in builtin/core.wren. Update all documentation files (classes.markdown, fiber.markdown, fn.markdown, sequence.markdown, error-handling.markdown, expressions.markdown, fibers.markdown, functions.markdown) to reflect the new constructor syntax, removing `new` keyword examples and replacing them with `ClassName.new()` patterns and `this new()` definitions.

test/core/function/arity.wren

@@ -1,5 +1,5 @@
-IO.print(new Fn {}.arity) // expect: 0
-IO.print(new Fn {|a| a}.arity) // expect: 1
-IO.print(new Fn {|a, b| a}.arity) // expect: 2
-IO.print(new Fn {|a, b, c| a}.arity) // expect: 3
-IO.print(new Fn {|a, b, c, d| a}.arity) // expect: 4
+IO.print(Fn.new {}.arity) // expect: 0
+IO.print(Fn.new {|a| a}.arity) // expect: 1
+IO.print(Fn.new {|a, b| a}.arity) // expect: 2
+IO.print(Fn.new {|a, b, c| a}.arity) // expect: 3
+IO.print(Fn.new {|a, b, c, d| a}.arity) // expect: 4

test/core/function/call_extra_arguments.wren

@@ -1,7 +1,7 @@
-var f0 = new Fn { IO.print("zero") }
-var f1 = new Fn {|a| IO.print("one ", a) }
-var f2 = new Fn {|a, b| IO.print("two ", a, " ", b) }
-var f3 = new Fn {|a, b, c| IO.print("three ", a, " ", b, " ", c) }
+var f0 = Fn.new { IO.print("zero") }
+var f1 = Fn.new {|a| IO.print("one ", a) }
+var f2 = Fn.new {|a, b| IO.print("two ", a, " ", b) }
+var f3 = Fn.new {|a, b, c| IO.print("three ", a, " ", b, " ", c) }
 
 f0.call("a") // expect: zero
 f0.call("a", "b") // expect: zero

test/core/function/call_missing_arguments.wren

@@ -1,2 +1,2 @@
-var f2 = new Fn {|a, b| IO.print(a, b) }
+var f2 = Fn.new {|a, b| IO.print(a, b) }
 f2.call("a") // expect runtime error: Function expects more arguments.

test/core/function/equality.wren

@@ -1,16 +1,16 @@
 // Not structurally equal.
-IO.print(new Fn { 123 } == new Fn { 123 })  // expect: false
-IO.print(new Fn { 123 } != new Fn { 123 })  // expect: true
+IO.print(Fn.new { 123 } == Fn.new { 123 })  // expect: false
+IO.print(Fn.new { 123 } != Fn.new { 123 })  // expect: true
 
 // Not equal to other types.
-IO.print(new Fn { 123 } == 1)         // expect: false
-IO.print(new Fn { 123 } == false)     // expect: false
-IO.print(new Fn { 123 } == "fn 123")  // expect: false
-IO.print(new Fn { 123 } != 1)         // expect: true
-IO.print(new Fn { 123 } != false)     // expect: true
-IO.print(new Fn { 123 } != "fn 123")  // expect: true
+IO.print(Fn.new { 123 } == 1)         // expect: false
+IO.print(Fn.new { 123 } == false)     // expect: false
+IO.print(Fn.new { 123 } == "fn 123")  // expect: false
+IO.print(Fn.new { 123 } != 1)         // expect: true
+IO.print(Fn.new { 123 } != false)     // expect: true
+IO.print(Fn.new { 123 } != "fn 123")  // expect: true
 
 // Equal by identity.
-var f = new Fn { 123 }
+var f = Fn.new { 123 }
 IO.print(f == f) // expect: true
 IO.print(f != f) // expect: false

test/core/function/new_wrong_arg_type.wren

@@ -1 +1 @@
-new Fn(3) // expect runtime error: Argument must be a function.
+Fn.new(3) // expect runtime error: Argument must be a function.

test/core/function/to_string.wren

@@ -1 +1 @@
-IO.print(new Fn {}) // expect: <fn>
+IO.print(Fn.new {}) // expect: <fn>

test/core/function/type.wren

@@ -1,4 +1,4 @@
-IO.print(new Fn { 0 } is Fn)      // expect: true
-IO.print(new Fn { 0 } is Object)  // expect: true
-IO.print(new Fn { 0 } is String)  // expect: false
-IO.print(new Fn { 0 }.type == Fn) // expect: true
+IO.print(Fn.new { 0 } is Fn)      // expect: true
+IO.print(Fn.new { 0 } is Object)  // expect: true
+IO.print(Fn.new { 0 } is String)  // expect: false
+IO.print(Fn.new { 0 }.type == Fn) // expect: true