Nanobind to dev

[DasVinch]

Complex PR with a number of things developed in the nanobind branch (a few of which reverted for dev) in synergy with the nanobind branch of pyMilk (https://github.com/milk-org/pyMilk/tree/nanobind) (which is to become pyMilk's dev branch soon).

The pyMilk nanobind branch wraps all of that in gcovr and provides testing and decent coverage (ImageStreamIO.c 43%; ImageStreamIOWrap.cpp 74%) of this merge.

Included:

• migrate python_module to nanobind away from pybind11

  • Same author, same philosophy
  • Compiles faster, less runtime overhead passing up and down from C
  • Buffer protocol doesn't exit anymore so we now have symmetric functions IMAGE.copy() and IMAGE.view() (zerocopy), and np.array(IMAGE) is disallowed.
  • The way time structs work, we may have lost some precision in some timestamps.
  • Overall binding is 200 lines shorter. Whatever but hey!

• Increase package version to 2.1 (not ImageStruct, still 1.0.3) [NO: that's the milk version, I got mixed up.]

• A couple missing const in some ISIO function signatures for strings

• Atomic creation of SHM files (creating under tmp filename, then atomic mv)

• refactor of destroyIm / closeIm so that destroyIm actually equals closeIm + extra work.

• Bug where image->used = 1; was never set in ImageStreamIO_read_sharedmem_image_toIMAGE (e.g. ImageStreamIO_openIm)

• GPU SHM: registry with refcount to manage multiple handles to the same GPU IPC segment within one process.

• GPU compilation: int IMAGESTRUCT_COMPILED_HAVE_CUDA = 0/1 for runtime checking of compilation if needed.

• Fix checkCudaError error print function

• Coverage build triggered with -DCMAKE_BUILD_TYPE=Coverage. For integration with the nox session "tests_run_coverage" of pyMilk which performs coverage over python and C/C++ files

Reverted - FYI (but present on nanobind brach):

• Addition of CLIcore_signals.h, 'milkDebugTools.h', timeutils.{c,h} --> helpful for restructuring milk v1 into a standalone package with processinfo and fps (see pyMilk under milkengine/ path).
• Changing the target to ImageStreamIOpyMilk for disambiguation at runtime linking.
• Changing the export symbols in CMakeLists. In the course of packaging a milkengine for pyMilk, I switched some target_include_directories from PUBLIC to PRIVATE. This means that #include "ImageStreamIO.h" is generally disallowed in the nanobind branch used by pyMilk, with #include "../ImageStreamIO/ImageStreamIO.h" required from sibling folders, or "ImageStreamIO/ImageStreamIO.h"` since the overall project root is on the include path.
  The current is:

target_include_directories(${LIBNAME} PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>
                                              $<INSTALL_INTERFACE:include/${SRCNAME}>
                                              $<INSTALL_INTERFACE:include>)

But I'd prefer to use:

target_include_directories(${LIBNAME} PRIVATE ${PROJECT_SOURCE_DIR})
target_include_directories(${LIBNAME} PUBLIC $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}>
                                             $<INSTALL_INTERFACE:include/${SRCNAME}>
                                             $<INSTALL_INTERFACE:include>)

[DasVinch]

No ABI changes.

@a-sevin @floferreira you may be interested.