[spec-model] Use `@apidevtools/swagger-parser`

[mikeharder]

Replace our custom zod schema with @apidevtools/swagger-parser:

azure-rest-api-specs/.github/shared/src/swagger.js

Lines 53 to 57 in 833aeb9

	// https://swagger.io/specification/v2/#swagger-object
	const swaggerSchema = z.object({
	paths: pathsSchema.optional(),
	"x-ms-paths": pathsSchema.optional(),
	});

This dependency is already used by oav, so it should handle all our existing swaggers.

WIP: https://github.com/mikeharder/azure-rest-api-specs/tree/spec-model-swagger-parser

Failing our unit tests, so maybe not worth migrating.