[TEST] Replace folded blocks with literal blocks

The regex tests are formatted with blocks for readability.  Previously,
they were formatted using folded style blocks (e.g. using `>`). Folded
blocks convert newlines into spaces.  This is problematic for our regex,
since comments can only be terminated with a newline.

Effectively, anything after a comment will be commented out, making many
of the regex "silently pass".

This commit replaces them with scalar-style blocks (e.g. using `|`), which
treats newlines as significant, and thus correctly terminates comments
inside the regex.

Also fixes a regex test (`cat.thread_pool/10_basic.yaml`) that started
to fail after the block was fixed.  The test was missing a `\s+` before
the closing newline.