Webpack: Set eslint plugin config to flat to prevent cli errors (#96199)

fix(webpack): set eslint plugin config to flat to prevent cli errors

packages/grafana-plugin-configs/webpack.config.ts

@@ -212,6 +212,7 @@ const config = async (env: Record<string, unknown>): Promise<Configuration> => {
                 path.basename(process.cwd()),
                 '.eslintcache'
               ),
+              configType: 'flat',
             }),
           ]
         : []),

scripts/webpack/webpack.dev.js

@@ -124,6 +124,7 @@ module.exports = (env = {}) => {
             cache: true,
             lintDirtyModulesOnly: true, // don't lint on start, only lint changed files
             extensions: ['.ts', '.tsx'],
+            configType: 'flat',
           }),
       new MiniCssExtractPlugin({
         filename: 'grafana.[name].[contenthash].css',