space-engine: add 'engine' attribute to space definition.

extra/schema_fill.lua

src/bootstrap.snap

src/box/alter.cc

src/box/key_def.cc

src/box/key_def.h

src/box/lua/schema.lua

src/box/lua/space.cc

src/box/schema.cc

src/box/space.cc

src/box/space.h

src/errcode.h

test/big/lua.result

test/box/alter.result

test/box/alter.test.lua

test/box/alter_limits.result

test/box/alter_limits.test.lua

test/box/misc.result

test/box/schema.result

test/box/temp_spaces.result

test/box/temp_spaces.test.lua