Poll support

[MinnDevelopment]

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Changes

• [ ] Internal code
• [x] Library interface (affecting end-user code)
• [ ] Documentation
• [ ] Other: _____

Closes Issue: #2646

Description

Adds support for message polls.

Reference: https://github.com/discord/discord-api-docs/pull/6746

Feature Additions

• MessagePoll
• MessagePollData
• MessagePollBuilder
• Message#getPoll()
• MessageCreateRequest#setPoll(MessagePollData)
• Message#replyPoll(MessagePollData)
• IReplyCallback#replyPoll(MessagePollData)
• MessageChannel#sendMessagePoll(MessagePollData)
• Message#endPoll()
• MessageChannel#endPollById(String)
• Message#retrievePollVoters(long)
• MessageChannel#retrievePollVoters(String|long, long)
• MessagePollAdd/RemoveEvent

Internal Additions

• Checks.notLonger(Duration, Duration, TimeUnit, String)

Test Additions

• <T>CheckAssertions
  A new way to test checks, similar to other assertion chains.
• AbstractSocketHandlerTest
  Tests for socket handlers

Example: Sending poll

channel.sendMessage("Hello guys! Check my poll:")
  .setPoll(
    MessagePollData.builder("Which programming language is better?")
      .addAnswer("Java", Emoji.fromFormatted("<:java:1006323566314274856>"))
      .addAnswer("Kotlin", Emoji.fromFormatted("<:kotlin:295940257797636096>"))
      .build())
  .queue()