Rework the HTTP Header Manager

Michael Osipov (Bug 62279): In the quest of BZ 62252 and BZ 62261 it turned out that the current HTTP Header Manager has some shortcomings.

• It is not possible to remove a header from being added via parent/child configuration
• It is not possible to have multiple header values.

We need basically to add a third column in the pane with the label "Action". An enum with "Add", "Replace" and "Remove".

"Add": Adds a header value even is already present in the parent or in the child. Multiple header values are valid according to RFC. "Replace": Replaces the (all) previous header value(s) with this value. "Remove": Removes one distinct matching header value or if left blank, all values.

There might be more cases.

See also:

• https://github.com/apache/jmeter/issues/5998

OS: All