Summary

• Quote string-like BSON values (Binary, ObjectId, RegularExpression, JavaScriptCode) in Document::toString() output so it produces valid JSON
• Previously, values like UUID(...), Base64 binary data, ObjectId hex strings, regex patterns, and JavaScript code were emitted unquoted, resulting in invalid JSON
• Add toString assertions to existing BSON tests to verify proper quoting

Test plan

• All 84 MongoDB tests pass (MongoDB-testrunner -all)
• Verified Binary (Base64 and UUID), ObjectId, RegularExpression, and JavaScriptCode produce quoted values
• Verified full Document::toString() output with these types is valid JSON