Support Forums: Update to reflect new Plugin Directory implementation

[coffee2code]

With the new Plugin Directory now live, the support forums need to be updated to pull data from the new site.

This includes updating the following functions to query against the new Plugin Directory WP tables:

• get_object_by_slug_and_type()
• get_authors()
• get_contributors()
• get_plugin_slugs_by_committer()
• get_plugin_slugs_by_contributor()

[coffee2code]

In 5286:

Support Forums: Update to query against the new Plugin Directory WP tables.

Updates get_object_by_slug_and_type(), get_authors(), get_contributors(), get_plugin_slugs_by_committer(), get_plugin_slugs_by_contributor().

Fixes #2701.

[coffee2code]

In 5287:

Support Forums, User Badges: Use get_authors() and get_contributors() from \WordPressdotorg\Forums\(Plugin|Theme) instance rather than duplicating their functionality.

See #2697, #2701.

[coffee2code]

In 5288:

Support Forums, User Badges: Use user_nicename instead of user_login when checking for user being an author or contributor.

See #2701.
Fixes #2697.

[coffee2code]

In 5301:

Support Forums: Search authors and contributors by user_nicename of user instead of user_login.

Fixes checks in user_can_resolve() and user_can_stick().

See #2701.
Fixes #2709.

[coffee2code]

In 5302:

Support Forums: get_authors() should return user_nicename value (rather than user_login) for theme author.

See #2701.