Change the built-in HTTP request validation to no longer use @kbn/config-schema

[kobelb]

At the moment, @kbn/config-schema is slow because Joi is admittedly slow, and not focused on increasing performance in the short-term: hapijs/joi#2340 (comment).

While performing some performance profiling for Fleet, I'm seeing around 6% of the total CPU time being spent validating the request. This CPU profile was captured after changing Fleet's custom route handling to no longer use @kbn/config-schema and almost all of the cost comes from the built-in HTTP request validation being dependent on Joi:

Prior to figuring out how to how to increase the performance of @kbn/config-schema, which is being tracked by #78351, we could potentially change the build-in HTTP request validation to no longer be based on @kbn/config-schema.

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

For information, even if we don't provide an alternative to config-schema, it is currently already possible to use a custom validation function for routing:

kibana/src/core/server/http/router/validator/validator.ts

Lines 98 to 114 in f593455

	export interface RouteValidatorConfig<P, Q, B> {
	/**
	* Validation logic for the URL params
	* @public
	*/
	params?: RouteValidationSpec<P>;
	/**
	* Validation logic for the Query params
	* @public
	*/
	query?: RouteValidationSpec<Q>;
	/**
	* Validation logic for the body payload
	* @public
	*/
	body?: RouteValidationSpec<B>;
	}

kibana/src/core/server/http/router/validator/validator.ts

Line 81 in f593455

export type RouteValidationSpec<T> = ObjectType | Type<T> | RouteValidationFunction<T>;

kibana/src/core/server/http/router/validator/validator.ts

Lines 61 to 72 in f593455

	export type RouteValidationFunction<T> = (
	data: any,
	validationResult: RouteValidationResultFactory
	) =>
	| {
	value: T;
	error?: never;
	}
	| {
	value?: never;
	error: RouteValidationError;
	};

[lizozom]

Duplicate of #78351
Closing this issue due to inactivity.
Feel free to reopen if needed 🙏🏻