feat: add poolUsage(s)/assetCount commands

[Lierrmm]

What does this PR do?

Adds 3 new commands that can be used for seeing the total number of xassets used.

• poolUsages
• poolUsage
• assetCount

How does this PR change IW4x's behaviour?

Existing behavior does not change.

• poolUsages

  • Lists the usage/total count of each xasset type

• poolUsage <number>

  • Lists the usage/total count of the specified xasset type

• assetCount

  • List the total amount of xassets used/total xasset limit

• poolUsages

• poolUsage <number>

• assetCount

Anything else we should know?

N/A

Did you check all the boxes?

• [x] Focus on a single fix or feature; remove any unrelated formatting or code changes
• [x] Mention any related issues (put closes #XXXX in comment to auto-close issue when PR is merged)
• [x] Follow our coding conventions
• [x] Minimize the number of commits

[Rackover]

@Lierrmm Hello, any news? 😄