libcamera: ipa_manager: implement class for managing IPA modules

IPAManager is a class that will search in given directories for IPA
modules, and will load them into a list. It also provides an interface
for pipeline handlers to acquire an IPA.

A meson build file for the IPAs is added, which also specifies a
hard-coded path for where to load the IPAs from in the installation
directory. More paths can be specified with the environment variable
LIBCAMERA_IPA_MODULE_PATH, with the same syntax as the regular PATH
environment variable. Make the test framework set this environment
variable.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

test/libtest/test.cpp

@@ -5,6 +5,8 @@
  * test.cpp - libcamera test base class
  */
 
+#include <stdlib.h>
+
 #include "test.h"
 
 Test::Test()
@@ -19,6 +21,10 @@ int Test::execute()
 {
 	int ret;
 
+	ret = setenv("LIBCAMERA_IPA_MODULE_PATH", "src/ipa", 1);
+	if (ret)
+		return errno;
+
 	ret = init();
 	if (ret)
 		return ret;