Avoid hard-coding "quantum" in `scripts/` scripts

[mhucka]

scripts/ci_validate_tutorials.sh has a hard-coded assumption that the user's local git working directory is named "quantum":

cd ..
examples_output=$(python3 quantum/scripts/test_tutorials.py)

This fails for developers who (like me) have multiple copies of the TFQ source tree, with different names for different concurrent development projects. Instead of assuming the directory is quantum, the scripts in the scripts/ directory should get the correct name using code such as the following:

thisdir=$(CDPATH="" cd -- "$(dirname -- "${0}")" && pwd -P)
repo_dir=$(git -C "${thisdir}" rev-parse --show-toplevel 2>/dev/null)

[Aniketsy]

I'll look into this and open PR shortly