feat(gen client): added support to work with multiple mimes

[fredbi]

• fixes request Content-Type isn't multipart/form-data #2773

1. fix: no longer sort producers and consumers
   The client runtime picks the first one, so the order is relevant.

2. feat: added extra options to set media type
   For client codegen only, AND whenever a single group of operations
   deals with more than one media for producers OR more than one media
   for consumers , THEN we generate an extra set of convenience ClientOption
   functions to switch media type.

   Generates generic options to set the mime as an arbitrary string
   (comes in handy to set mime extensions):

   WithContentType(string) (to negotiate consumers)
   WithAccept(string) (to negotiate producers)

   Generate shorthands with a mangled name such as:
   WithContentTypeApplicationxWwwFormUrlencoded
   to be used directly as an option.

• Simple APIs with a single producer and a single consumer are not
  affected.

• Server codegen is not affected

• test: content type is not sorted

• test: asserted codegen

NOTE: see #2773 on github issues for a complete analysis.
The part of that issue relative to the runtime client not supporting
file upload with application/x-www-form-urlencoded is obviously not
fixed by this PR.

Signed-off-by: Frédéric BIDON fredbi@yahoo.com

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (876c950) 0.00% compared to head (0b235d0) 0.00%.

❗ Current head 0b235d0 differs from pull request most recent head f494956. Consider uploading reports for the commit f494956 to get more accurate results

Additional details and impacted files

@@      Coverage Diff       @@
##   master   #3042   +/-   ##
==============================
==============================

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.