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/azure-devops/azure-devops-base.js

@@ -1,8 +1,7 @@
 'use strict'
 
 const Joi = require('joi')
-const BaseJsonService = require('../base-json')
-const { NotFound } = require('../errors')
+const { BaseJsonService, NotFound } = require('..')
 
 const latestBuildSchema = Joi.object({
   count: Joi.number().required(),

services/azure-devops/azure-devops-build.service.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const BaseSvgService = require('../base-svg-scraping')
-const { NotFound } = require('../errors')
+const { NotFound } = require('..')
 const { keywords, fetch } = require('./azure-devops-helpers')
 const { renderBuildStatusBadge } = require('../../lib/build-status')
 

services/azure-devops/azure-devops-build.tester.js

@@ -6,7 +6,7 @@ const { isBuildStatus } = require('../../lib/build-status')
 // https://dev.azure.com/totodem/Shields.io is a public Azure DevOps project
 // solely created for Shields.io testing.
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('default branch')
   .get(

services/azure-devops/azure-devops-coverage.tester.js

@@ -53,7 +53,7 @@ const secondLinesCovStat = {
 const expCoverageSingleReport = '83%'
 const expCoverageMultipleReports = '77%'
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('default branch coverage')
   .get(`${uriPrefix}/${linuxDefinitionId}.json`)

services/azure-devops/azure-devops-release.tester.js

@@ -6,7 +6,7 @@ const { isBuildStatus } = require('../../lib/build-status')
 // https://dev.azure.com/totodem/Shields.io is a public Azure DevOps project
 // solely created for Shields.io testing.
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('release status is succeeded')
   .get(

services/azure-devops/azure-devops-tests.tester.js

@@ -113,7 +113,7 @@ const isCompactCustomAzureDevOpsTestTotals = isAzureDevOpsTestTotals(
   true
 )
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('unknown build definition')
   .get(`${uriPrefix}/${nonExistentDefinitionId}.json`)