StereoDepth: mesh rectification, disp/depth configurable resolution

[alex-luxonis]

• StereoDepth mesh rectification support, mainly for fisheye camera usecase. The left and right meshes (files or byte arrays) need to be configured in the pipeline.
• disparity/depth configurable output resolution, by rescaling the output. Available for now only when RGB-depth alignment is enabled (a warning is issued otherwise). For example, aligning ColorCamera preview and disparity/depth is possible as:

// Center cropping with no distortion
colorCamera->setPreviewKeepAspectRatio(true)  // Also default
colorCamera->setPreviewSize(300, 300)
stereoDepth->setOutputKeepAspectRatio(true)   // Also default
stereoDepth->setOutputSize(300, 300)

or

// No cropping on ColorCamera (the image will get squished). 
// Slight cropping may be applied to disparity/depth to get it aligned, as the RGB FOV is narrower
colorCamera->setPreviewKeepAspectRatio(false)
colorCamera->setPreviewSize(300, 300)
stereoDepth->setOutputKeepAspectRatio(false)
stereoDepth->setOutputSize(300, 300)

• rgb_depth_aligned example: lower mono camera resolution for now: 720p -> 400p, to fix the lag, while keeping 30fps. The alignment will be further optimized in the future.

Related PR: luxonis/depthai-shared#36

[SzabolcsGergely]

Style check is failing

[SzabolcsGergely]

Open PR for python bindings

[alex-luxonis]

Updated PR description with snippets for using the new StereoDepth API: setOutputSize (renamed from setOutputResolution) and setKeepAspectRatio.