internal/civisibility: add support for unskippable tests and suites

[tonyredondo]

What does this PR do?

This PR adds support for marking tests or suites as unskippable by the Intelligent Test Runner.

• A suite is marked as unskippable if at the top of the file the //dd:suite.unskippable comment is found.
• A single test is marked as unskippable if the test function is marked with //dd:test.unskippable comment.

The notation was inspired by Orchestrion custom span notation: https://datadoghq.dev/orchestrion/docs/custom-trace/#creating-custom-trace-spans

Motivation

This is part of the specification for Intelligent Test Runner: https://datadoghq.atlassian.net/wiki/spaces/SDTEST/pages/3123348305/Intelligent+Test+Runner+in+CI+Visibility+Libraries#Unskippable-tests

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.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-10-31 10:34:29

Comparing candidate commit 273d27f in PR branch tony/civisibility-unskippable-test-and-suite with baseline commit 59f9f97 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 58 metrics, 1 unstable metrics.