Implement Bun.YAML.stringify (#22183)

### What does this PR do?
This PR adds `Bun.YAML.stringify`. The stringifier will double quote
strings only when necessary (looks for keywords, numbers, or containing
non-printable or escaped characters). Anchors and aliases are detected
by object equality, and anchor name is chosen from property name, array
item, or the root collection.
```js
import { YAML } from "bun"

YAML.stringify(null) // null
YAML.stringify("hello YAML"); // "hello YAML"
YAML.stringify("123.456"); // "\"123.456\""

// anchors and aliases
const userInfo = { name: "bun" };
const obj = { user1: { userInfo }, user2: { userInfo } };
YAML.stringify(obj, null, 2);
// # output
// user1: 
//   userInfo: 
//     &userInfo
//     name: bun
// user2: 
//   userInfo: 
//     *userInfo

// will handle cycles
const obj = {};
obj.cycle = obj;
YAML.stringify(obj, null, 2);
// # output
// &root
// cycle:
//   *root

// default no space
const obj = { one: { two: "three" } };
YAML.stringify(obj);
// # output
// {one: {two: three}}
```

### How did you verify your code works?
Added tests for basic use and edgecases

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- New Features
- Added YAML.stringify to the YAML API, producing YAML from JavaScript
values with quoting, anchors, and indentation support.

- Improvements
- YAML.parse now accepts a wider range of inputs, including Buffer,
ArrayBuffer, TypedArrays, DataView, Blob/File, and SharedArrayBuffer,
with better error propagation and stack protection.

- Tests
- Extensive new tests for YAML.parse and YAML.stringify across data
types, edge cases, anchors/aliases, deep nesting, and round-trip
scenarios.

- Chores
- Added a YAML stringify benchmark script covering multiple libraries
and data shapes.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/string.zig

@@ -866,19 +866,8 @@ pub const String = extern struct {
             bun.assert(index < this.length());
         }
         return switch (this.tag) {
-            .WTFStringImpl => if (this.value.WTFStringImpl.is8Bit()) @intCast(this.value.WTFStringImpl.utf8Slice()[index]) else this.value.WTFStringImpl.utf16Slice()[index],
-            .ZigString, .StaticZigString => if (!this.value.ZigString.is16Bit()) @intCast(this.value.ZigString.slice()[index]) else this.value.ZigString.utf16Slice()[index],
-            else => 0,
-        };
-    }
-
-    pub fn charAtU8(this: String, index: usize) u8 {
-        if (comptime bun.Environment.allow_assert) {
-            bun.assert(index < this.length());
-        }
-        return switch (this.tag) {
-            .WTFStringImpl => if (this.value.WTFStringImpl.is8Bit()) this.value.WTFStringImpl.utf8Slice()[index] else @truncate(this.value.WTFStringImpl.utf16Slice()[index]),
-            .ZigString, .StaticZigString => if (!this.value.ZigString.is16Bit()) this.value.ZigString.slice()[index] else @truncate(this.value.ZigString.utf16SliceAligned()[index]),
+            .WTFStringImpl => if (this.value.WTFStringImpl.is8Bit()) this.value.WTFStringImpl.latin1Slice()[index] else this.value.WTFStringImpl.utf16Slice()[index],
+            .ZigString, .StaticZigString => if (!this.value.ZigString.is16Bit()) this.value.ZigString.slice()[index] else this.value.ZigString.utf16Slice()[index],
             else => 0,
         };
     }
@@ -1178,10 +1167,6 @@ pub const SliceWithUnderlyingString = struct {
         return this.utf8.slice();
     }
 
-    pub fn sliceZ(this: SliceWithUnderlyingString) [:0]const u8 {
-        return this.utf8.sliceZ();
-    }
-
     pub fn format(self: SliceWithUnderlyingString, comptime fmt: []const u8, opts: std.fmt.FormatOptions, writer: anytype) !void {
         if (self.utf8.len == 0) {
             try self.underlying.format(fmt, opts, writer);