infof: remove newline from format strings, always append it

infof: remove newline from format strings, always append it

- the data needs to be "line-based" anyway since it's also passed to the
  debug callback/application

- it makes infof() work like failf() and consistency is good

- there's an assert that triggers on newlines in the format string

- Also removes a few instances of "..."

- Removes the code that would append "..." to the end of the data *iff*
  it was truncated in infof()

Closes #7357