Update submodules to latest releases/branches.

pybind11 2.6.1.
spdlog 1.8.2

autocheck and googletest to latest main branches.

autocheck @ ef501a73

-Subproject commit 9a4f2bc839ead140bb7201052c69809943ca5b30
+Subproject commit ef501a7310621c710984b1e1dfd5b746077a0e83

googletest @ 389cb68b

-Subproject commit 9ab640ce5e5120021c5972d7e60f258bfca64d71
+Subproject commit 389cb68b87193358358ae87cc56d257fd0d80189

pybind11 @ f1abf5d9

-Subproject commit 9a19306fbf30642ca331d0ec88e7da54a96860f9
+Subproject commit f1abf5d9159b805674197f6bc443592e631c9130

spdlog @ de0dbfa3

-Subproject commit cf6f1dd01e660d5865d68bf5fa78f6376b89470a
+Subproject commit de0dbfa3596a18cd70a4619b6a9766847a941276