dash: switch to reusable license workflow and externalize dash tool (#842)

- Use reusable GitHub Actions workflow for license checks
- Migrate dash license checker to Bazel registry; remove local tooling

Addresses: #813

Signed-off-by: Dan Calavrezo <dan.calavrezo.ext@qorix.ai>

Author: dcalavrezo-qorix

tooling/docs/_tooling/docs.bzl

@@ -45,7 +45,6 @@ load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
 load("@rules_python//python:pip.bzl", "compile_pip_requirements")
 load("@rules_python//sphinxdocs:sphinx.bzl", "sphinx_build_binary", "sphinx_docs")
 load("//docs:_tooling/extensions/score_source_code_linker/collect_source_files.bzl", "parse_source_files_for_needs_links")
-load("//tools/dash:dash.bzl", "dash_license_checker")
 load("//tools/testing/pytest:defs.bzl", "score_py_pytest")
 
 sphinx_requirements = all_requirements + [