feat(Shard): shard-specific broadcastEval/fetchClientValues + shard Id util

[MattIPv4]

Please describe the changes this PR makes and why it should be merged:

Adds the ability to call broadcastEval and fetchClientValues from a shard to run on different target shard, instead of broadcasting to all and using an if in the given script to filter by shard.

Now you can target a shard directly:

const { ShardClientUtil } = require('discord.js');
const guild = '433980600391696384';

// Get the shard Id -- `client.shard.constructor.shardIdForGuildId` could also be used
const shard = ShardClientUtil.shardIdForGuildId(guild, 2);

// Get the guild from that shard only
const name = await client.shard.broadcastEval(`this.guilds.cache.get('${guild}').name`, shard);

return [name, shard, client.shardId];

We get back [JetBrains Community, 1, 0], so we can see it correctly went to the target shard and found the guild there.

Status

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

Semantic versioning classification:

• This PR changes the library's interface (methods or parameters added)
  • This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
• This PR only includes non-code changes, like changes to documentation, README, etc.

[jonahsnider]

Code probably works but I have a few minor suggestions with the shardIdForGuildId function.

[jonahsnider]

New edits look good.

[SpaceEEC]

Otherwise LGTM

Stale