Add flatpak module and state

[EllisGoodman]

What does this PR do?

Adds a new execution module and a new state module for managing flatpak packages and flatpak remotes.

Note that there was a previous PR for flatpak support: #51993. It was never merged into master, though. There was also #56907 but it had no outcome either. The code in this PR is based on #51993 with substantial changes and modernization.

What issues does this PR fix or reference?

None

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

[welcome]

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[twangboy]

@EllisGoodman Starting in Salt 3008 and forward Salt has removed non-core Execution and State modules. Non-core modules are to be supported by the community. There is a GitHub org set up for this purpose: https://github.com/salt-extensions. This code would be better served as a salt-extension.

There is currently discussion and work being done on the salt-extensions Discord channel (https://discordapp.com/channels/1200072194781368340/1208165123240370197) to document and build the infrastructure for community-supported salt extensions. There is also a Salt-Extensions Working Group that takes place on the 1st and 3rd Thursday of every month to coordinate salt-extension efforts.

Please consider creating a salt-extension for this code and join the community in supporting the development and testing of salt-extensions.