feat: check for disabled renovate.json (#4114)

lib/platform/azure/azure-helper.ts

lib/platform/azure/index.ts

lib/platform/bitbucket-server/README.md

lib/platform/bitbucket-server/index.ts

lib/platform/bitbucket/index.ts

lib/platform/common.ts

test/platform/azure/azure-helper.spec.ts

test/platform/azure/index.spec.ts

...latform/bitbucket-server/__snapshots__/index.spec.ts.snap

test/platform/bitbucket-server/index.spec.ts

test/platform/bitbucket/_fixtures/responses.js

test/platform/bitbucket/index.spec.ts