Duplicate `http.server.middleware` spans emitted for Next.js middleware

[chargome]

Description

Our nextjs sdk emits two http.server.middleware spans for a single middleware request:

• Parent (is_segment: true / is_transaction: true): name middleware GET <route> - the OTel Middleware.execute transaction (correct).
• Child: name http.server.middleware, description middleware, origin auto.function.nextjs.wrap_middleware- redundant, overlaps the parent, no useful attributes or children.

This affects webpack only as we do not instrument middleware on turbopack.

[linear-code]

JS-3172

[Lms24]

related: #21718

@chargome when tackling this, can we settle on either http.server or middleware as a span op? The mixture between the two is a bit problematic for span streaming / description inference

[chargome]

@Lms24 Yes' I'll do both in one go. I'd go for middleware?

[Lms24]

Sounds great, thanks!