Optimize size and performance of images used in running QA tests on GDK

Proposal

As part of gitlab-org/quality/quality-engineering&4 (closed) we're runing end-to-end (QA) tests on GDK in MRs and in master pipelines.

Earlier work provides an MVC with very large docker images. This issue proposes some options for reducing the image size and job times.

Tasks

• Consider if we can enable incremental webpack compilation, or precompile.

Subsequent work

• Consider if GDK build caches can be saved outside the GDK container and shared between master and MR pipelines.
• Consider in webpack cache can be stored outside the container and shared between master and MR pipelines.