remove echo statements in tests (part 1)

[ringabout]

Too many echo statements in the results of megatests, which is hard to debug and reason with.

It helps https://github.com/nim-lang/Nim/pull/19972

Imo lots of echo are unnecessary and has some substitutes:

• echo "ok" at the end of the file is unnecessary
• echo can be replaced with doAssert in many cases

[ringabout]

This PRs focus on some simple cases where echos are at the end of the tests in most cases.

[github-actions[bot]]

Thanks for your hard work on this PR! The lines below are statistics of the Nim compiler built from 3dbf2ac9469bdaaf876f902242a883fe1847adf0

Hint: mm: orc; threads: on; opt: speed; options: -d:release 163627 lines; 12.230s; 841.371MiB peakmem