chore: bump testcontainers-go to 0.18.0

[mdelapenya]

• Closes #

Required checklist

• Sample config files updated (both /etc folder and NewDemoConfig methods) (influxdb and plutonium)
• openapi swagger.yml updated (if modified API) - link openapi PR
• Signed CLA (if not already signed)

Description

1-3 sentences describing the PR (or link to well written issue)

This PR is bumping the testcontainers-go dependency from 0.15.0 to the recently released 0.18.0

Context

Why was this added? What value does it add? What are risks/best practices?

Keep dependencies up-to-date.
Given the usage is narrowed down to one single place, the risks of a breakage are very low.

Note for reviewers:

Check the semantic commit type:

• Feat: a feature with user-visible changes
• Fix: a bug fix that we might tell a user “upgrade to get this fix for your issue”
• ✅ Chore: version bumps, internal doc (e.g. README) changes, code comment updates, code formatting fixes… must not be user facing (except dependency version changes)
• Build: build script changes, CI config changes, build tool updates
• Refactor: non-user-visible refactoring
• Check the PR title: we should be able to put this as a one-liner in the release notes