Add RHEL 10 (UBI) support for connect (Standard/Minimal)

[bschwedler]

Phase 2 of the RHEL 10 (UBI) initiative (posit-dev/images-shared#575).

Connect has no RHEL/UBI support today — this is first-time enablement,
not a port of an existing pattern. posit-dev/images-package-manager#130
(RHEL 10 UBI support) is the closest precedent: Containerfile.rhel10.std/min,
deps/rhel-10_packages.txt, and an install script wired through the shared
dnf.j2 macro.

Approach

• Standard and Minimal builds on registry.access.redhat.com/ubi10/ubi,
  amd64 + arm64
• Validate R, Python, and Quarto install and run correctly on RHEL 10
  (requires R 4.6.1+ to avoid the flexiblas-devel issue fixed in
  Allow RHEL RPMs to work on UBI 9/10: make flexiblas-devel a weak dependency rstudio/r-builds#329)
• Fix the RHEL 10 gap in posit_product/main.py's distro-tag resolver
  (ProductEnum.CONNECT branch handles versions 8/9 but falls through to
  "multi" for 10)

Notes

Out of scope: connect-content/connect-content-init (tracked
separately).