Return a couple additional ArrayPoolLists

[benaadams]

Very minor

Changes

• Dispose two additional ArrayPoolLists
• Refactor existing ones to use using
• Use ArrayPool<T>.Shared directly rather than storing in field (Jit can then devirtualise)

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

[asdacap]

LGTM