to-do: investigate the viability of `ParseOptions` and `StringifyOptions` in `@std/yaml`

[iuioiua]

These interfaces have a lot of options, and each added option means more engineering overhead for both users and maintainers. We should go over each option and only keep the ones that have sufficient justifications for existing.

ParseOptions:

• [x] legacy (removed in #5229)
• [x] listener (removed in #5224)
• [x] filename (removed in #5223)
• [x] schema
• [ ] json
• [ ] onWarning

StringifyOptions (currently DumpOptions but to be updated in the next release):

• [ ] indent
• [ ] noArrayIndent
• [ ] skipInvalid
• [ ] flowLevel
• [ ] styles
• [x] schema
• [ ] sortKeys
• [ ] lineWidth
• [ ] noRefs
• [ ] noCompatMode (removed in #5233)
• [ ] condenseFlow

[iuioiua]

ParseOptions.json allows parse() to behave similarly to JSON.parse(), in that duplicate keys are overwritten rather than throwing errors. This goes against the YAML 1.2 spec, which states that duplicate keys should cause errors (see here and here). Do we want to remove the ability to have this functionality (AKA remove ParseOptions.json) or keep it? @kt3k