contrib/packaging/docker/rhel9

interfaces: introduce and use a protocol class for the `charencoding` module

See f2832de2a46c for details when this was done for the `bdiff` module.

This lets us dump the hack where the `pure` implementation was imported during
the type checking phase to provide signatures for the module methods it
provides.  Now the protocol classes are starting to shine, because these methods
are provided by `pure.charencoding` and `cext.parsers`, and references to
`cffi.charencoding` and `cext.charencoding` are forwarded to them as appropriate
by the `policy` module.  But none of that matters, as long as the module
returned provides the listed methods.

The interface was copy/pasted from the `pure` module, but `jsonescapeu8fallback`
is omitted because it is accessed from the `pure` module directly when the
escaping fails in the primary module's `jsonescapeu8()`.

FROM rockylinux/rockylinux:9

RUN groupadd -g %GID% build && \
    useradd -u %UID% -g %GID% -s /bin/bash -d /build -m build

RUN dnf install 'dnf-command(config-manager)' -y
# crb repository is necessary for docutils
RUN dnf config-manager --set-enabled crb

RUN yum install -y \
	gcc \
	gettext \
	make \
	python3-devel \
	python3-docutils \
	rpm-build

# For creating repo meta data
RUN yum install -y createrepo

# For rust extensions
RUN yum install -y cargo

# avoid incorrect docker image permissions on /tmp preventing writes by non-root users
RUN chmod 1777 /tmp