Make `http -f` display the request headers. Closes #9912 #9633

Job	Run time
std-lib-and-python-virtualenv (ubuntu-20.04, py)	4m 37s
std-lib-and-python-virtualenv (macos-latest, py)	6m 42s
std-lib-and-python-virtualenv (windows-latest, py)	8m 50s
tests (windows-latest, default)	14m 24s
tests (macos-latest, default)	7m 37s
tests (ubuntu-20.04, default)	5m 15s
tests (ubuntu-20.04, dataframe)	7m 56s
tests (ubuntu-20.04, extra)	6m 19s
plugins (windows-latest)	5m 10s
plugins (macos-latest)	3m 36s
plugins (ubuntu-20.04)	1m 16s
fmt-clippy (windows-latest, default)	4m 48s
fmt-clippy (windows-latest, extra)	7m 52s
fmt-clippy (macos-latest, default)	1m 57s
fmt-clippy (macos-latest, extra)	5m 7s
fmt-clippy (ubuntu-20.04, default)	1m 9s
fmt-clippy (ubuntu-20.04, dataframe)	1m 11s
fmt-clippy (ubuntu-20.04, extra)	1m 4s
	1h 34m 50s

Provide feedback