Feature/467450 - Edge GraphQL query & services updates (#692)

Functional changes:
* Update introspection, and connected/disconnected GraphQL components in Next sample to account for latest Edge scheme. The change is that `language` is required in all queries. This fixes the broken build.

Non-functional devEx improvements:
* Add CacheClient and GraphQLClient interfaces to allow implementations to override which 3rd party libs are used by services.
* Pull shared functionality related to using `search` query (ie handling pagination) into new SearchQueryService; update GraphQLDictionaryService and SitemapService to use this service.
* Make it easier to customize our services by changing access level of methods from private to protected

Misc changes:
* [sitecore-jss] Move app root query functionality from /utils to /graphql
* Fix typo in docs

docs/data/routes/docs/nextjs/getting-started-nextjs/walkthrough-jsscreate/en.md

@@ -38,7 +38,7 @@ To create a JSS application, you must:
    npm install -g @sitecore-jss/sitecore-jss-cli
    ```
 
-   > To verify the successful installation of the JSS CLI and to see the list of commands availably globally, run `jss --help`.
+   > To verify the successful installation of the JSS CLI and to see the list of commands availability globally, run `jss --help`.
 
 3. Run:
 

packages/sitecore-jss-nextjs/src/services/component-props-service.ts

@@ -85,7 +85,7 @@ export class ComponentPropsService {
    * @param {NextContext} context next context
    * @returns {Promise<ComponentPropsCollection>} component props
    */
-  private async fetchComponentProps<NextContext>(
+  protected async fetchComponentProps<NextContext>(
     fetchFunctionFactory: FetchFunctionFactory<NextContext>,
     layoutData: LayoutServiceData,
     context: NextContext
@@ -112,7 +112,7 @@ export class ComponentPropsService {
    * @param {ComponentPropsRequest<NextContext>[]} params.requests
    * @returns {ComponentPropsRequest<NextContext>[]} array of requests
    */
-  private collectRequests<NextContext>(params: {
+  protected collectRequests<NextContext>(params: {
     placeholders?: PlaceholdersData;
     fetchFunctionFactory: FetchFunctionFactory<NextContext>;
     layoutData: LayoutServiceData;
@@ -158,7 +158,7 @@ export class ComponentPropsService {
    * @param {ComponentPropsRequest<NextContext>[]} requests requests
    * @returns {Promise<ComponentPropsCollection>} requests result
    */
-  private async execRequests<NextContext>(
+  protected async execRequests<NextContext>(
     requests: ComponentPropsRequest<NextContext>[]
   ): Promise<ComponentPropsCollection> {
     const componentProps: ComponentPropsCollection = {};
@@ -211,7 +211,7 @@ export class ComponentPropsService {
    * @param {PlaceholdersData} placeholders placeholders
    * @returns {ComponentRendering[]} renderings
    */
-  private flatRenderings(placeholders: PlaceholdersData): ComponentRendering[] {
+  protected flatRenderings(placeholders: PlaceholdersData): ComponentRendering[] {
     const allComponentRenderings: ComponentRendering[] = [];
     const placeholdersArr = Object.values(placeholders);