Move build.sh execution from within rpm %posttrans script to
it's own dedicated rockstor-build.service. Enabling greater
fidelity and control over the environment and timing; and eases
development and user feedback on build.sh failures in the future.

Partnered with rockstor.spec changes in rockstor-rpmbuild repo.

## Includes
- New rockstor-build.service file.
- After= & Requires= entries in rockstor-pre on rockstor-build,
to extend our service cascade.
- Trivial build.sh and pkg_mgmt.py comment updates.
- Add the new rockstor-build.service to initrock.py to assist
in asserting the service akin to all other rockstor services.
Mostly redundant given our rpm service management, but nice-to-have.

…md-service

Add rockstor-build systemd service #2793

Introduce 'poetry-plugin-dotenv' to enable Poetry to establish
environmental variables from a .env file. Add PASSWORD_STORE_DIR &
DJANGO_SETTINGS_MODULE variables to inform OS level 'password-store'
app, & our .venv Django of their configuration.

## Includes:
- Additional logging to poetry-install.txt to indicate plugins installed.
- Include new `.env` file in project.toml for sdist inclusion.
- NO SECRETS indicator in new .env file.
- Add `source .env` to build.sh to ease development, the .env file is
also read by build.sh's dedicated rockstor-build.service.
- Pin, in build.sh, poetry-plugin-dotenv to latest 0.6.11
- Adopt new `poetry run mnt-share share-name`, with required `cd`, in
new `root preexec` Samba share config creation.
- Incidentally fix legacy Poetry removal regression introduced when
build.sh execution was moved to a systemd service from rpm %posttrans.
- Add smb.conf preexec migration procedure to initrock.
- Remove redundant smb & nmb restarts from prior preexec migrations.
- Resource .env file in all relevant rockstor*.service files
via `EnvironmentFile=` directive.
- Normalise on `/usr/local/bin/poetry run` script invocation
in all relevant rockstor*.service files.
- Modify developer instructions (build.sh) to account for new
poetry-plugin-dotenv.

…essible-5.0.6-0-&-5.0.7-0

(t) Samba shares not accessible - 5.0.6-0 & 5.0.7-0 #2794

pyproject.toml build.sh

…-base---testing-branch

Bump versions to a 5.0.8 base - testing branch #2800