Revert "reader: read and read-string are read-eval safe, added unsafe-read and unsafe-read-string"

This reverts commit 2899201a9f4e6bcda1dd5beca6606206cde3ec75.
Revert "test: more test to ensure safety of read and read-string"

This reverts commit c57495d360b47c92bb5751966ea83f7d5815814d.