Align swift-tools-version across all packages

[ncreated]

What and why?

📦 Fixing the problem revealed in recent nightly tests failure:

xcodebuild: error: Could not resolve package dependencies:
  package 'testutilities' is using Swift tools version 5.7.0 but the installed version is 5.6.0

How?

Following this post from Apple:

Starting April 25, 2022, iOS, iPadOS, and watchOS apps submitted to the App Store must be built with Xcode 13 (...)

it makes sense to align all our packages with:

// swift-tools-version: 5.5

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference
• Add CHANGELOG entry for user facing changes

Custom CI job configuration (optional)

• Run unit tests
• Run integration tests
• Run smoke tests

[maxep]

Thanks 👍

[datadog-datadog-prod-us1]

Datadog Report

Branch report: ncreated/fix-nightly-builds
Commit report: adfe2fb

✅ dd-sdk-ios: 0 Failed, 0 New Flaky, 116 Passed, 0 Skipped, 4m 30.78s Wall Time