[Enhancement]: Shrink size of core-jar / Rethink shading

Module

Core

Proposal

The testcontainers jar file currently has a size of a whopping 17MB (packed; unpacked 34MB), making it by far one of the biggest maven dependencies I know of.

Most of the size (>97%; 33MB) seems to come from shaded artifacts inside org.testcontainers.shaded.

A full list of disadvantages of shading can be found in JLBP-18.

I think the jar could be a lot smaller. Here a few ways how this could be tackled:

• Check if all the shaded dependencies are required in the core module in the first place. I check the core module and couldn't find any class that implements: org.hamcrest, org.checkerframework, org.bouncycastle or org.awaitability.
  There are also other libraries that could be easily replaced, e.g. guava as it's only used in a few places and uses nowadays standard java stuff. Removing these 5 libs alone would shrink the lib by 23MB or 67% alone.
• Maybe don't use shading at all and publish a bom that contains the exact versions of the required dependencies, that way there should also be no dependency conflicts

Start in the Core module and inspect how shaded artifacts are declared and packaged into the testcontainers jar. Review which listed dependencies are required, measure the packed and unpacked jar sizes, and compare the shading and BOM approaches. Done means a decided dependency strategy that reduces the core jar without breaking its consumers.