[B+C] Add entry-related methods to scoreboard API. Adds BUKKIT-5779

[caseif]

The Issue:

Most methods in the scoreboard API which pertain to OfflinePlayer have been deprecated in favor of the use of entries. However, some methods remain without an entry-related alternative.

Justification:

If OfflinePlayers in relation to the scoreboard API are to be deprecated, the change should be thorough and offer an alternative for all methods.

PR Breakdown:

Add getEntryTeam(String) to Scoreboard.class
Add getEntries(), addEntry(String), removeEntry(String), and hasEntry(String) to Team.class
Deprecate getPlayerTeam(OfflinePlayer) in Scoreboard.class
Deprecate getPlayers(), addPlayer(OfflinePlayer), removePlayer(OfflinePlayer), and hasPlayer(OfflinePlayer) in Team.class

Testing Results and Materials:

The new scoreboard API methods function as expected when employed in a basic plugin.

Relevant PRs:

CB-1410

JIRA Ticket:

BUKKIT-5779