libvirt: Version bump to 11.9.0, split out variants, add startup items

[iamGavinJ]

Description

Version bump to 11.9.0
Additionally variants for bhyve, esx, test, vbox, and vmware have been added, and also set at default variants as to not break prior installs.
Startup items have been created for libvirt daemons.

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 15.7.2 24G325 arm64
Xcode 26.0.1 17A400

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@ryandesign for port libvirt.