Add Testconainers support

[wurzelkuchen]

To make working in encapsulated environments/containers more easy, we should add testcontainers to neodymium.

Work so far:
We already created a proof of concept which can be found in the branch testcontainer_playground. Have a specific look at the following commits:

• (https://github.com/Xceptance/neodymium-library/commit/33bcc7a8a75e2a769e443f00fcf80806a4bcc6a0)
• (https://github.com/Xceptance/neodymium-library/commit/33bcc7a8a75e2a769e443f00fcf80806a4bcc6a0)

Requirements:

• a user should be able to toggle the usage of testcontainers on and off via configuration
• this should support all of our supported browsers

Additionally:

• research ways to make it possible to watch a browser performing a test with testcontainers

[wurzelkuchen]

Please also check how testcontainers and services like browserstack interact. If those don't work together we might need to add assertions so users don't activate both at the same time and crash or get unexpected results.