[Key Vault] Use the swagger generated from the service 7.2-preview

[sadasant]

As the title says.

JSON files come from: https://raw.githubusercontent.com/Azure/azure-rest-api-specs/master/specification/keyvault/data-plane/Microsoft.KeyVault/preview/7.2-preview/

swagger README should look along the lines of:

package-name: "@azure/keyvault-admin"
use-extension:
  "@autorest/typescript": "6.0.0-dev.20200623.2"
azure-arm: false
generate-metadata: false
add-credentials: false
license-header: MICROSOFT_MIT_NO_VERSION
input-file:
  - https://raw.githubusercontent.com/Azure/azure-rest-api-specs/master/specification/keyvault/data-plane/Microsoft.KeyVault/preview/7.2-preview/rbac.json
source-code-folder-path: ./src/generated

The package.json command should look like:

    "regenerate": "npx autorest swagger/README.md --typescript --version=3.0.6267",

The core folder should be named generated.

[ramya-rao-a]

Please use v5 of the code generator for this task to reduce the amount of code changes this late in the sprint cycle.
We can use v6 as part of #9590

[sadasant]

@ramya-rao-a Moved this to September, based on the latest meeting that Heath had. We're only shipping 7.1 stuff in July.

[sadasant]

Just to reiterate, for @autorest/typescript v6 and autorest v3 we have this other issue: #9590