Release candidate v2.19.0-rc.1

Noteworthy changes since the previous release:

• added support for initial autosetup of isolated_cores (rhbz#2093847)
• net: added MTU support (rhbz#2082494)
• openshift: added support for NVMe devices
• bootloader: do not hardcode disk name in tuned initrd path (rhbz#2050246)
• fixed parsing of inline comments (rhbz#2060138)
• added support for quotes in isolated_cores specification (rhbz#1891036)
• spec: reduced weak dependencies (rhbz#2093841)
• recommend: do not ignore syspurpose_role if there is no syspurpose (rhbz#2030580)
• bootloader: cmdline parser fixed escaping (rhbz#1884472)
• documentation: added inline ASCIIDOC description into the plugins code
• realtime: set tsc as 'reliable'
• bash: fixed autocomplete