Support discriminator with no parent/shared properties

[sserrata]

Description

See #1026 for background.

Motivation and Context

OpenAPI spec allows for defining discriminator schemas with no shared/parent properties. This PR adds support for this pattern by merging the discriminator property from mapped schemas into the parent.

[github-actions]

Size Change: +3.08 kB (+0.15%)

Total Size: 2.02 MB

Filename	Size	Change
demo/.docusaurus/globalData.json	39 kB	+426 B (+1.1%)
demo/.docusaurus/registry.js	57.5 kB	+619 B (+1.09%)
demo/.docusaurus/routes.js	53.1 kB	+558 B (+1.06%)
demo/.docusaurus/routesChunkNames.json	22 kB	+240 B (+1.1%)
demo/build/assets/js/main.********.js	693 kB	+1.14 kB (+0.16%)
demo/build/assets/js/runtime~main.********.js	15.3 kB	+100 B (+0.66%)

ℹ️ View Unchanged

Filename	Size
demo/.docusaurus/codeTranslations.json	2 B
demo/.docusaurus/docusaurus.config.mjs	13.9 kB
demo/.docusaurus/i18n.json	267 B
demo/.docusaurus/site-metadata.json	1.23 kB
demo/build/assets/css/styles.********.css	146 kB
demo/build/index.html	90.4 kB
demo/build/petstore/add-pet/index.html	27.4 kB
demo/build/petstore/create-user/index.html	21.5 kB
demo/build/petstore/create-users-with-array-input/index.html	21.5 kB
demo/build/petstore/create-users-with-list-input/index.html	21.5 kB
demo/build/petstore/delete-order/index.html	21.5 kB
demo/build/petstore/delete-pet/index.html	21.6 kB
demo/build/petstore/delete-user/index.html	21.8 kB
demo/build/petstore/find-pets-by-status/index.html	22.3 kB
demo/build/petstore/find-pets-by-tags/index.html	22.9 kB
demo/build/petstore/get-inventory/index.html	20.8 kB
demo/build/petstore/get-order-by-id/index.html	21.8 kB
demo/build/petstore/get-pet-by-id/index.html	22.4 kB
demo/build/petstore/get-user-by-name/index.html	21.9 kB
demo/build/petstore/login-user/index.html	22.4 kB
demo/build/petstore/logout-user/index.html	21.2 kB
demo/build/petstore/new-pet/index.html	21.8 kB
demo/build/petstore/pet/index.html	23.5 kB
demo/build/petstore/place-order/index.html	21 kB
demo/build/petstore/schemas/apiresponse/index.html	22.8 kB
demo/build/petstore/schemas/cat/index.html	36.7 kB
demo/build/petstore/schemas/category/index.html	23.9 kB
demo/build/petstore/schemas/dog/index.html	37.1 kB
demo/build/petstore/schemas/honeybee/index.html	37.2 kB
demo/build/petstore/schemas/id/index.html	20.9 kB
demo/build/petstore/schemas/order/index.html	25 kB
demo/build/petstore/schemas/pet/index.html	36.6 kB
demo/build/petstore/schemas/tag/index.html	22.3 kB
demo/build/petstore/schemas/user/index.html	44.8 kB
demo/build/petstore/store/index.html	21.5 kB
demo/build/petstore/subscribe-to-the-store-events/index.html	27.8 kB
demo/build/petstore/swagger-petstore-yaml/index.html	27.8 kB
demo/build/petstore/update-pet-with-form/index.html	21.7 kB
demo/build/petstore/update-pet/index.html	22.2 kB
demo/build/petstore/update-user/index.html	21.8 kB
demo/build/petstore/upload-file/index.html	21.6 kB
demo/build/petstore/user/index.html	22.4 kB

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[github-actions]

Visit the preview URL for this PR (updated for commit 1db55c9):

https://docusaurus-openapi-36b86--pr1040-e49f1ave.web.app

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