common: remove "_pool_" from API names

benchmarks/blk_mt/blk_mt.c

benchmarks/log_mt/log_mt.c

benchmarks/vmem_mt/vmem_mt.c

doc/libvmem.3

examples/libpmemblk/assetdb/asset_checkout.c

examples/libpmemblk/assetdb/asset_load.c

src/blk.c

src/include/libpmemblk.h

src/include/libpmemlog.h

src/include/libpmemobj.h

src/include/libvmem.h

src/libpmemblk.map

src/libpmemlog.map

src/libpmemobj.map

src/libvmem.map

src/log.c

src/obj.c

src/test/Makefile

src/test/blk_nblock/README

src/test/blk_nblock/blk_nblock.c