remove React's FC type from codebase (#3527)

* WIP-packages: remove React's FC type from codebase

* remove FC from other directories

* fix build failures

* add types to required packages

docs/api/utility-apis.md

@@ -33,10 +33,10 @@ hook exported by `@backstage/core`, or the `withApis` HOC if you prefer class
 components. For example, the `ErrorApi` can be accessed like this:
 
 ```tsx
-import React, { FC } from 'react';
+import React from 'react';
 import { useApi, errorApiRef } from '@backstage/core';
 
-export const MyComponent: FC<{}> = () => {
+export const MyComponent = () => {
   const errorApi = useApi(errorApiRef);
 
   // Signal to the app that something went wrong, and display the error to the user.

docs/reference/createPlugin-feature-flags.md

@@ -27,7 +27,7 @@ To inspect the state of a feature flag inside your plugin, you can use the
 `FeatureFlagsApi`, accessed via the `featureFlagsApiRef`. For example:
 
 ```tsx
-import React, { FC } from 'react';
+import React from 'react';
 import { Button } from '@material-ui/core';
 import { featureFlagsApiRef, useApi } from '@backstage/core';
 

docs/tutorials/quickstart-app-plugin.md

@@ -81,13 +81,13 @@ import { useApi } from '@backstage/core-api';
 _from inline:_
 
 ```tsx
-const ExampleComponent: FC<{}> = () => ( ... )
+const ExampleComponent = () => ( ... )
 ```
 
 _to block:_
 
 ```tsx
-const ExampleComponent: FC<{}> = () => {
+const ExampleComponent = () => {
 
     return (
         ...
@@ -135,7 +135,7 @@ changes, let's start by wiping this component clean.
 1. Replace everything in the file with the following:
 
 ```tsx
-import React, { FC } from 'react';
+import React from 'react';
 import { useAsync } from 'react-use';
 import Alert from '@material-ui/lab/Alert';
 import {
@@ -147,7 +147,7 @@ import {
 import { useApi } from '@backstage/core-api';
 import { graphql } from '@octokit/graphql';
 
-const ExampleFetchComponent: FC<{}> = () => {
+const ExampleFetchComponent = () => {
   return <div>Nothing to see yet</div>;
 };
 
@@ -223,7 +223,7 @@ type DenseTableProps = {
   viewer: Viewer;
 };
 
-export const DenseTable: FC<DenseTableProps> = ({ viewer }) => {
+export const DenseTable = ({ viewer }: DenseTableProps) => {
   const columns: TableColumn[] = [
     { title: 'Name', field: 'name' },
     { title: 'Created', field: 'createdAt' },