ipa: Switch to the plain C API

Switch IPA communication to the plain C API. As the IPAInterface class
is easier to use for pipeline handlers than a plain C API, retain it and
add an IPAContextWrapper that translate between the C++ and the C APIs.

On the IPA module side usage of IPAInterface may be desired for IPAs
implemented in C++ that want to link to libcamera. For those IPAs, a new
IPAInterfaceWrapper helper class is introduced to wrap the IPAInterface
implemented internally by the IPA module into an ipa_context,
ipa_context_ops and ipa_callback_ops.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

Documentation/Doxyfile.in

@@ -793,6 +793,7 @@ WARN_LOGFILE           =
 
 INPUT                  = "@TOP_SRCDIR@/include/ipa" \
 			 "@TOP_SRCDIR@/include/libcamera" \
+			 "@TOP_SRCDIR@/src/ipa/libipa" \
 			 "@TOP_SRCDIR@/src/libcamera" \
 			 "@TOP_BUILDDIR@/include/libcamera" \
 			 "@TOP_BUILDDIR@/src/libcamera"

Documentation/meson.build

@@ -24,6 +24,8 @@ if doxygen.found()
                       libcamera_ipa_api,
                       libcamera_headers,
                       libcamera_sources,
+                      libipa_headers,
+                      libipa_sources,
                   ],
                   output : 'api-html',
                   command : [doxygen, doxyfile],