refactor: fromVersion -> currentVersion (#8709)

docs/usage/self-hosted-configuration.md

lib/config/migration.ts

lib/manager/common.ts

lib/manager/npm/index.ts

...nager/pip_requirements/__snapshots__/extract.spec.ts.snap

lib/manager/pip_requirements/extract.ts

lib/util/cache/repository/index.spec.ts

lib/util/cache/repository/index.ts

lib/util/package-rules.spec.ts

lib/util/package-rules.ts

lib/util/template/index.ts

lib/versioning/cargo/index.spec.ts

lib/versioning/cargo/index.ts

lib/versioning/common.ts

lib/versioning/composer/index.spec.ts

lib/versioning/composer/index.ts

lib/versioning/docker/index.spec.ts

lib/versioning/gradle/index.spec.ts

lib/versioning/hashicorp/index.spec.ts

lib/versioning/hashicorp/index.ts