Add Python bindings

Add libcamera Python bindings. pybind11 is used to generate the C++ <->
Python layer.

We use pybind11 'smart_holder' version to avoid issues with private
destructors and shared_ptr. There is also an alternative solution here:

https://github.com/pybind/pybind11/pull/2067

Only a subset of libcamera classes are exposed. Implementing and testing
the wrapper classes is challenging, and as such only classes that I have
needed have been added so far.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

subprojects/.gitignore

@@ -1,3 +1,4 @@
 /googletest-release*
 /libyuv
-/packagecache
+/packagecache
+/pybind11

subprojects/packagefiles/pybind11/meson.build

@@ -0,0 +1,7 @@
+project('pybind11', 'cpp',
+    version : '2.9.1',
+    license : 'BSD-3-Clause')
+
+pybind11_incdir = include_directories('include')
+
+pybind11_dep = declare_dependency(include_directories : pybind11_incdir)

subprojects/pybind11.wrap

@@ -0,0 +1,9 @@
+[wrap-git]
+url = https://github.com/pybind/pybind11.git
+# This is the head of 'smart_holder' branch
+revision = aebdf00cd060b871c5a1e0c2cf4a333503dd0431
+depth = 1
+patch_directory = pybind11
+
+[provide]
+pybind11 = pybind11_dep