Create shortcut for BaseService-related imports (#2809)

Continue to implement #2698:

- Add `core/base-service/index.js` (but hold off on moving the things it imports)
- Add shortcuts in `services/index.js` for Base*Service, errors, and deprecatedService. This file will be streamlined later to avoid cluttering it with rarely used bits.
- Apply consistent ordering of imports and use of `module.exports` in testers.
- Remove some renaming of imports.
- Remove obsolete tests here and there.

services/codacy/codacy-coverage.service.js

@@ -4,8 +4,8 @@ const Joi = require('joi')
 const {
   coveragePercentage: coveragePercentageColor,
 } = require('../../lib/color-formatters')
-const BaseSvgScrapingService = require('../base-svg-scraping')
-const { NotFound } = require('../errors')
+const { BaseSvgScrapingService } = require('..')
+const { NotFound } = require('..')
 
 const schema = Joi.object({
   message: Joi.alternatives()

services/codacy/codacy-coverage.tester.js

@@ -3,7 +3,7 @@
 const Joi = require('joi')
 const { isIntegerPercentage } = require('../test-validators')
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('Coverage')
   .get('/59d607d0e311408885e418004068ea58.json')

services/codacy/codacy-grade.service.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const Joi = require('joi')
-const BaseSvgScrapingService = require('../base-svg-scraping')
+const { BaseSvgScrapingService } = require('..')
 const { codacyGrade } = require('./codacy-helpers')
 
 const schema = Joi.object({ message: codacyGrade }).required()

services/codacy/codacy-grade.tester.js

@@ -3,7 +3,7 @@
 const Joi = require('joi')
 const { codacyGrade } = require('./codacy-helpers')
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('Code quality')
   .get('/grade/e27821fb6289410b8f58338c7e0bc686.json')