To make special newlines more explicit and visible.
Mostly in `<protocol>` sections, some in `<data*>` and `<upload>`.
Reducing the number of `tests/data/test*`:
- CRLF newlines from 21535 to 11337.
- files with mixed newlines from 1335 to 707.
Also delete empty `<protocol>` sections.
Closes#19284
Split out adding of individual request headers into a switch. Check
the connection http version only on fresh connections, use separate
methods.
Add TE: header directly without allocation. Add bit for indicating
Connection: header has been added and custom headers should not do
that again.
Closes#18444
