[core] Improve AssertionUtil messages

[adangel]

Describe the PR

We sometimes don't give much info, when we reach an assertion.
Especially for #4885, we don't preserve the original exception.
I've updated a couple of places, where we throw AssertionUtil.shouldNotReachHere.

Related issues

• Ref [java] AssertionError: Method should be accessible #4885
  • added a simple test case. At least, we exercise the code path, but the problem is not reproducible.

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by github actions)
• Added (in-code) documentation (if needed)

[pmd-test]

	1 Message
📖	Compared to master: This changeset changes 0 violations, introduces 0 new violations, 0 new errors and 0 new configuration errors, removes 0 violations, 0 errors and 0 configuration errors. Download full report as build artifact

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