Resync with latest version in pub
Support string entry containing quotes, commas and \n.

Some entry (delimited by separator) can contains commas and \n altogether. They
are delimited by quotes. Ensure we merged them to the previous content with an
entry have, for instance this layout:
foo1,"foo2\nfoo3,fo"o4",foo5. The resulting list will then be:
[foo1, foo2\nfoo3,fo"o4, foo5].
Some content can be empty, don't throw at them.

Some lines (especially when contained with quotes delimiters) can be empty
line. Drop the thowing exception to support them. In case we do have empty
lines un unquotted sequence, the result will be some empty list of strings,
which matches the reality.