Simplify the version bump process. ### Description

Simplify the version bump process.

- Use substitution hook in docs to update CDN URL.
  - In `dev` or `prerelease` versions, it will point to `dev` url
  - In `stable` versions, it will point it `vX.Y.Z` url
- Introduce a version bump script `tools/bump_version.py`.


~- Use `bump2version` to bump Python versions (continuing from #2460)~
~- Use `npm version` to bump JS versions~
~- Update `run_docker` script to use latest deployed pre-built docker image when `--pre-built` option is specified.~

### Checklists

- [x] Add new / update outdated documentation

package:
  name: cycler
  version: 0.11.0
source:
  url: https://files.pythonhosted.org/packages/5c/f9/695d6bedebd747e5eb0fe8fad57b72fdf25411273a39791cde838d5a8f51/cycler-0.11.0-py3-none-any.whl
  sha256: 3a27e95f763a428a739d2add979fa7494c912a32c17c4c38c4d5f082cad165a3
test:
  imports:
    - cycler
requirements:
  run:
    - six

package:
  name: cycler
  version: 0.11.0
source:
  url: https://files.pythonhosted.org/packages/5c/f9/695d6bedebd747e5eb0fe8fad57b72fdf25411273a39791cde838d5a8f51/cycler-0.11.0-py3-none-any.whl
  sha256: 3a27e95f763a428a739d2add979fa7494c912a32c17c4c38c4d5f082cad165a3
test:
  imports:
    - cycler
requirements:
  run:
    - six
