Adds a run-plugin operator to HRW

[zwoop]

An example use case is to conditionally enable / run the rate_limit.so plugin for some requests:

cond %{REMAP_PSEUDO_HOOK} [AND]
cond %{CLIENT-HEADER:X-Leif} ="yes"
     run-plugin rate_limit.so "--limit=300 --error=429"

[ywkaras]

Can this run on any hook other than the remap hook?

[zwoop]

No it can only run in a remap hook, but the plugin it runs can setup other hooks.

[ywkaras]

Testing schmesting I guess.

[shukitchan]

actually there is something wrong with the test.

but basically with the plugin factory, you can achieve this anywhere else, like Lua plugin or txn_box

[ywkaras]

I'll be on vacation for 2 weeks after today, so I'll I have to leave any further review to others. Looks OK from a quick read through.

[zwoop]

Testing schmesting I guess.

Yeh, well... I can't reproduce the build problem on either my Mac or my Linux box, but seems like it may be that the header_rewrite_test target needs a score dependency?

[zwoop]

[approve ci]

[shukitchan]

Just curious. should we pass on the return status of the doRemap() function somewhere?

[shukitchan]

Now it is just ignored.

[zwoop]

Yeh, so we kinda butchered this a bit in all the refactoring and dealings with "chaining" remap plugins. In most cases, this return code is obsoleted, and we don't' really use it. So, I made a choice to ignore it in HRW, whereas in Cripts, the caller can chose to look at it and do something with it (albeit, I think that's unlikely).

I'm not sure the stop / continue works any more either, but almost no plugin that's in use uses that.

[cmcfarlen]

Cherry-picked to v10.0.x