Recent maturin version and standardizing Python across GH workflows

[dvmarcilio]

Changes

• pyproject.toml: Bump maturin to latest version (taken from their documentation)
• build workflow:
  • python setup before any python command
  • py version 3.8 (from #417)
• release workflow: setup-python v4 (same as build)
• RELEASING.md:
  • fix in push step
  • markdown fixes
• CHANGELOG.md: pointing out that version 0.3.23 may not install some Linux versions (see below for more details)

Tests

• GitHub build workflow
• Following RELEASING.md steps in local environment:
  • ubuntu
  • macOS

Context

643's pyproject.toml is only supported by more recent versions of maturin.

Currently, by running pip install maturin, we use the latest 1.4.0 version in local development, most of GitHub workflows, and in RELEASING.md. However, pyproject.toml was specifying version 0.13.0 for maturin, which raised a warning (e.g., build for #643 , build for #632):

Warning: You specified maturin >=0.13, <0.14 in pyproject.toml under build-system.requires, but the current maturin version is 1.4.0

So after #634, we had a build problem for specific ubuntu version when maturin version was indeed 0.13.0. The build problem seems to be flaky, as #634's build passed, but following ones did not. Moreover, I successfully locally built releases from macOS and another ubuntu version.

The changes in polyglot_build.yml and polyglot_release.yml aim to remove this python and python-dependencies inconsistencies.