Reduce type duplication by excluding undefined

[Mrtenz]

This is intended to be merged into @legobeat's branch (#134).

[legobeat]

Result from dist/types/json.d.ts after yarn build:

export declare const JsonRpcRequestStruct: Struct<{
    id: string | number | null;
    method: string;
    jsonrpc: "2.0";
    params?: Json[] | Record<string, Json> | undefined;
}, {
    id: Struct<string | number | null, null>;
    jsonrpc: Struct<"2.0", "2.0">;
    method: Struct<string, null>;
    params: Struct<Json[] | Record<string, Json> | undefined, null>;
}>;
export declare type InferWithParams<Type extends Struct<any>, Params extends JsonRpcParams> = Omit<Infer<Type>, 'params'> & {
    params?: Exclude<Params, undefined>;
};
/**
 * A JSON-RPC request object.
 */
export declare type JsonRpcRequest<Params extends JsonRpcParams = JsonRpcParams> = InferWithParams<typeof JsonRpcRequestStruct, Params>;
export declare const JsonRpcNotificationStruct: Struct<{
    method: string;
    jsonrpc: "2.0";
    params?: Json[] | Record<string, Json> | undefined;
}, {
    jsonrpc: Struct<"2.0", "2.0">;
    method: Struct<string, null>;
    params: Struct<Json[] | Record<string, Json> | undefined, null>;
}>;

[legobeat]

Looking good:

• TEST: @metamask/utils patch a00dfc9d9bfcc3215161124d9b1f4dd6009e831c  core#1641
• [DONOTMERGE]: Validate MetaMask/utils#135 rpc-errors#105
• TEST: Patch @metamask/utils v8.0.0 with https://github.com/MetaMask/utils/pull/135 eth-json-rpc-middleware#239
• DONOTMERGE: bump @metamask/rpc-errors to 5.1.1 patched with MetaMask/rpc-errors/pull/102 (utils #135) json-rpc-engine#163

[legobeat]

This is now part of #134