rpm-ostree: Dedupe major version check using AppStreamIntegration

AppStreamIntegration: Allow overriding DistroComponentId

On Fedora Kinoite, currentDistroComponentId will get an ID that includes AppStreamIntegration: Allow overriding DistroComponentId

On Fedora Kinoite, currentDistroComponentId will get an ID that includes the variant (Kinoite) and thus does not match the ID of Fedora that we are using for all major version checks.

This will be used in the rpm-ostree backend.

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AppStreamIntegration: Add hidden option to enable updates to development versions

We currently have the AllowPreRelease hidden option that enables updating to AppStream::Kind "Developement" releases which is used for Fedora pre-releases such as Fedora 40 Beta.

Add an hidden option to enable updates to development versions (i.e Rawhide for Fedora), which are AppStream::Snapshot.

Example ~/.config/discoverrc config:

[DistroUpgrade]
AllowPreRelease=true
AllowDevelopmentRelease=true

This will be used in the rpm-ostree backend.

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rpm-ostree: Load AppStream pool async

Do not block the main thread while loading the AppStream pool.

Copied from the PackageKit backend.

Commit diff best viewed with space changes ignored.

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rpm-ostree: Dedupe major version check using AppStreamIntegration

Share the major version check code with the existing code in AppStreamIntegration used by the PackageKit backend (which was inspired by this original code).

Example ~/.config/discoverrc config:

[DistroUpgrade]
AllowPreRelease=true
AllowDevelopmentRelease=true

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rpm-ostree: Hidden option to skip "pending update before rebase" check

Removes the previously commented debugging code and add an hidden environment variable to enable skipping the "pending update before rebase" check to help with development for major version rebases.

Use export DISCOVER_RPM_OSTREE_DEVEL=1 to use it.