contrib/gofiber/fiber.v2: add possibility to exclude spans generation for specific requests

[nsakharenko]

What does this PR do?

Thi PR is about adding functionality to gofiber trace Middleware to avoid span generation for a specific requests.

Motivation

Exclude spans generation for unneeded endpoints, like /healthcheck, /, /version etc. and to be able to do it on an application level rather than DD Agent.

Issue

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

For Datadog employees:

• If this PR touches code that handles credentials of any kind, such as Datadog API keys, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[darccio]

LGTM

[rarguelloF]

LGTM!