Make update.sh work with RHEL-based distros

[egg82]

The following changes are made:

• Uses /etc/os-release to determine OS type
• Uses command -v dnf to determine if dnf is available, and falls back to yum if not
• Uses yum/dnf in place of apt and apt-get where applicable
• Trades apt keyrings for yum GPG keys where applicable
• Changes www-data for nginx user/group where applicable
• Installs pango and pango-devel from proper sources when in a RHEL environment
• Uses pyenv to install proper python version when in RHEL environment
• Uses proper nodejs setup script and dnf/yum install when in a RHEL environment
• Changes python manage.py to python3.11 manage.py to be consistent
• Changes /etc/nginx/sites-available to /etc/nginx/conf.d when in a RHEL environment
• Fixes the directory permissions of all of the parent directories for /rmm/api/tacticalrmm/tacticalrmm.sock (nginx can't access socket)

The biggest change is the use of pyenv which required editing the service files, but it works well. This change could easily be added to the Debian section if desired, which would be less work than manually compiling the version each time.

[CLAassistant]

All committers have signed the CLA.