Upgrade to latest stable Poetry

[phillxnet]

Poetry has just had a new stable release of 1.8.*, it is proposed that we update out pinning to this latest stable version of 1.8.2.

We now install our Poetry via OS provided pipx (py3.11 variant via alternatives) and so according to the blog post for this main release:

https://python-poetry.org/blog/announcing-poetry-1.8.0/

We can, on systems with our prior 1.7.1 Poetry installed (testing channel only still) do the following:

pipx upgrade poetry

• It is unclear as of yet if this will also install the new version on systems upgrading from our master (stable) branch.
• The interaction with our newly introduced 'pipx inject poetry-plugin-dotenv' poetry plugin is also unclear. However this plugin has also been updated a number of times to now be in-line with the newer stable Poetry release. We pinned this plugin via:

pipx inject --verbose poetry poetry-plugin-dotenv==0.6.11

in build.sh

And so we will also need the appropriate pipx upgrade/reinstall command for the newer version of this plugin: currently at 0.6.19: https://pypi.org/project/poetry-plugin-dotenv/

Upstream history: https://python-poetry.org/history/