dillon1000/react

[Flight] Only skip past the end boundary if there is a newline character (#26945)

Follow up to #26932

For regular rows, we're increasing the index by one to skip past the
last trailing newline character which acts a boundary. For length
encoded rows we shouldn't skip an extra byte because it'll leave us
missing one.

This only accidentally worked because this was also the end of the
current chunk which tests don't account for since we're just passing
through the chunks. So I added some noise by splitting and joining the
chunks so that this gets tested.