feat: additional pullsync handler metrics

[ldeffenb]

Checklist

• [x] I have read the coding guide.
• [x] My change requires a documentation update, and I have done it.
• [x] I have added tests to cover my changes.
• [x] I have filled out the description and linked the related issues.

Description

Adding Offer and Want metrics on the handler side of pullsync to match the ones already available on the client side of the protocol.

Open API Spec Version Changes (if applicable)

N/A

Motivation and Context (Optional)

With only "Sent" metrics on the handler side, you cannot see the peer-generated load of offering chunks via pullsync.

Related Issue (Optional)

N/A

Screenshots (if appropriate):