Motivation: Currently we have to manually update the all_tests variable
when introducing new test files.
Fix: I've modified it to list test files dynamically, but rather than
modify it to add all test files, I've first modified it to only add test
files from the following 4 paths so that it doesn't deviate too much
from what we already do
- unit
- unit/type
- unit/cluster
- integration
Related issue: https://github.com/valkey-io/valkey/issues/302
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Signed-off-by: jonghoonpark <dev@jonghoonpark.com>