Completed parsing filelists.xml and combined it with the primary parser in class MetadataParser

[waterflow80]

What does this PR change?

• Created a parser for filelists.xml
• Created a MetadataParser that uses both PrimaryParser and FilelistsParser to parse and build rpm packages' metadata

GUI diff

No difference.

Before:

After:

• [x] DONE

Documentation

• No documentation needed: only internal and user invisible changes

• [x] DONE

Test coverage

• No tests: still in progress

• [x] DONE

Links

Issue(s): # Port(s): # add downstream PR(s), if any

• [x] DONE

Changelogs

Make sure the changelogs entries you are adding are compliant with https://github.com/uyuni-project/uyuni/wiki/Contributing#changelogs and https://github.com/uyuni-project/uyuni/wiki/Contributing#uyuni-projectuyuni-repository

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Re-run a test

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• [ ] Re-run test "changelog_test"
• [ ] Re-run test "backend_unittests_pgsql"
• [ ] Re-run test "java_pgsql_tests"
• [ ] Re-run test "schema_migration_test_pgsql"
• [ ] Re-run test "susemanager_unittests"
• [ ] Re-run test "javascript_lint"
• [ ] Re-run test "spacecmd_unittests"

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