CLEANUP: Scrutinize helperGetPluginStore and relative duplication

[kalnode]

Eliminate duplicated logic between src/plugins/eimu/server/services/init.ts and src/plugins/eimu/server/services/configure-indexing.ts

This also means figuring out the TS issue:

// ERROR:
// > strapi ts:generate-types

// Error: Could not load js config file /Users/kal/Projects/sportpost/socialmeet/src/plugins/strapi-plugin-elasticsearch/strapi-server.js: Cannot read properties of undefined (reading 'services')
// at loadJsFile (/Users/kal/Projects/sportpost/socialmeet/node_modules/@strapi/strapi/dist/core/app-configuration/load-config-file.js:18:13)
// at Module.loadFile (/Users/kal/Projects/sportpost/socialmeet/node_modules/@strapi/strapi/dist/core/app-configuration/load-config-file.js:37:14)
// at Object.loadPlugins (/Users/kal/Projects/sportpost/socialmeet/node_modules/@strapi/strapi/dist/core/loaders/plugins/index.js:90:41)
// at async Strapi.loadPlugins (/Users/kal/Projects/sportpost/socialmeet/node_modules/@strapi/strapi/dist/Strapi.js:311:5)
// at async Promise.all (index 3)
// at async Strapi.register (/Users/kal/Projects/sportpost/socialmeet/node_modules/@strapi/strapi/dist/Strapi.js:341:5)
// at async action (/Users/kal/Projects/sportpost/socialmeet/node_modules/@strapi/strapi/dist/commands/actions/ts/generate-types/action.js:12:15)

// * The terminal process "/bin/zsh '-c', 'npm run 'strapi gen typings''" terminated with exit code: 1.
// * Terminal will be reused by tasks, press any key to close it.