fix: Add support for Open API discriminator on anyOf/oneOf

[heath-freenome]

Reasons for making this change

Fixes #3512 by updating the getFirstMatchingOption() and getClosestMatchingOption() to take an optional discriminator property to use for drilling into one-of Objects to simplify selection detection and using that in MultiSchemaField by passing the propertyName of a discriminator if it exists.
Fixes #2044 Fixing the toIdSchema() generation to use the getSchemaType() function rather than just using schema.type

• In @rjsf/utils, updated the SchemaUtilsType, its associated class implementation and several functions to fix both bug as follows:
  • Updated SchemaUtilsType to add an optional discriminatorField?: string parameter to the get(First|Closest|)MatchingOption() functions
  • Updated createSchemaUtils() to take the new discriminatorField parameter and forward it onto the underlying function `get(First|Closest|)MatchingOption() implementations
  • Updated the getClosestMatchingOption() and getFirstMatchingOption() to pass the new discriminatorField to the getMatchingOption() function
  • Updated getMatchingOption() to use discriminatorField when it is present in the options object properties to drill into the object to detect if that one field is valid
  • Also updated the toIdSchemaInternal() function to use getSchemaType(schema) === 'object' rather than schema.type === 'object' to get the proper pathing for ids
• In @rjsf/core, updated the MultiSchemaField, to get the discriminator.propertyName value for a anyOf/oneOf object and pass it into getClosestMatchingOption()
  • Updated the oneOf and anyOf tests to verify the discriminator property works
  • Also updated the oneOf and form tests to update the few ids that were fixed by the toIdSchema() fix
  • Moved a test that was once just in the bootstrap-4 theme related to additionalProperties being defined as true for a non-object type schema
• In the other themes, updated the snapshots to include the new test that was moved from bootstrap-4 into the objectTests
  • Updated bootstrap-4 to delete the AdditionalProperties.test.tsx and its associated snapshot since it was moved to core
• Updated the utility-functions documentation to add the new discriminatorField prop to the get(First|Closest|)MatchingOption() functions
• Updated the CHANGELOG.md file accordingly

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests. I've run npm run test:update to update snapshots, if needed.
  • I've updated docs if needed
  • I've updated the changelog with a description of the PR
• I'm adding a new feature
  • I've updated the playground with an example use of the feature