Ability to pass in JSON schema on McpServer

[felixweinberger]

Allow passing JSON schema directly on the higher-order McpServer abstraction.

Part of v2 SDK work.

[MaxKless]

yes please this is highly needed. I essentially have to drop down to the lower-level abstraction in order to use JSON schema directly even though that's what the spec uses

[KKonstantinov]

This is done in #1689, closing