Rename relay::Environment to relay::Module (#2054)

include/tvm/relay/base.h

include/tvm/relay/build_module.h

include/tvm/relay/expr.h

include/tvm/relay/interpreter.h

include/tvm/relay/module.h

include/tvm/relay/pass.h

include/tvm/relay/type.h

python/tvm/relay/__init__.py

python/tvm/relay/_ir_pass.pyi

python/tvm/relay/_module.py

python/tvm/relay/_module.pyi

python/tvm/relay/build_module.py

python/tvm/relay/expr.py

python/tvm/relay/interpreter.py

python/tvm/relay/ir_pass.py

python/tvm/relay/module.py

src/relay/interpreter.cc

src/relay/ir/module.cc

src/relay/ir/text_printer.cc

src/relay/pass/fuse_ops.cc