Add capsule flatpak e2e case

[vsedmik]

Problem Statement

6.17 Capsule is going to support the flatpak content so we should have an E2E case to cover that.

Solution

This PR adds such a case. It also adds a flatpak_remote fixture I plan to use elsewhere.

Related Issues

https://issues.redhat.com/browse/SAT-23287

PRT test Cases example

trigger: test-robottelo
pytest: tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library
Katello:
    katello: 11264

[vsedmik]

trigger: test-robottelo
pytest: tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library
Katello:
    katello: 11264

[Satellite-QE]

PRT Result

Build Number: 9901
Build Status: UNSTABLE
PRT Comment: pytest tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library --external-logging
Test Result : ========== 1 failed, 28 deselected, 48 warnings in 5716.31s (1:35:16) ==========

[vsedmik]

trigger: test-robottelo
pytest: tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library

[Satellite-QE]

PRT Result

Build Number: 9980
Build Status: UNSTABLE
PRT Comment: pytest tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library --external-logging
Test Result : ========== 1 failed, 28 deselected, 46 warnings in 1608.18s (0:26:48) ==========

[vsedmik]

PRT failed due to this issue: https://issues.redhat.com/browse/SAT-30541
It is fixed in smart_proxy_container_gateway-3.2.0 which is not yet in snap 86.

[vsedmik]

rebased

[vsedmik]

trigger: test-robottelo
pytest: tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library

[Satellite-QE]

PRT Result

Build Number: 10033
Build Status: SUCCESS
PRT Comment: pytest tests/foreman/cli/test_capsulecontent.py -k test_sync_consume_flatpak_repo_via_library --external-logging
Test Result : ========== 1 passed, 28 deselected, 48 warnings in 2161.39s (0:36:01) ==========