* [REFACTOR][TYPE] Finish move all types to IR.

- Move definition of Ref and TensorType to ir
- Move type_functor.h to public header.
- Rename RefType -> RelayRefType for clarity.

* Add atol

- Use consistent constructor style to construct objects.
- Move env_func to ir as it is mainly used to construct IRs.
- Make docs consistent.

This PR brings relay::Module as the unified IRModule structure.
IRModule will be used as the basic unit for transformations
through out the stack.

- Rename relay::Module -> IRModule
- Move relay/module.h -> ir/module.h
- ModuleNode::FromExpr -> IRModule::FromExpr
- FromText -> IRModule::FromText

Under the unified IR. We will allow a single IRModule
to store different function variants, such as relay::Function,
ExternFunc, and low-level function.

This PR changes relay::Function -> BaseFunc in the module file
to support multiple function variants.

* [REFACTOR] relay::Module Def -> TypeDef

The term Def was not very clear about what is the object of interest(could be function def or type def).
Changes the term to TypeDef to be more explicit.

* Update include/tvm/relay/module.h

Co-Authored-By: Wei Chen <ipondering.weic@gmail.com>

Co-authored-by: Wei Chen <ipondering.weic@gmail.com>

TVM_REGSISTER_API is an alias of TVM_REGISTER_GLOBAL.
In the spirit of simplify redirections, this PR removes
the original TVM_REGISTER_API macro and directly use TVM_REGISTER_GLOBAL.

This type of refactor will also simplify the IDE navigation tools
such as FFI navigator to provide better code reading experiences.

Move EnvFunc's definition to node.

* [REFACTOR][OBJECT] Consoldiate NodePtr/Ref/Hash/Equal and macros to Object.

Historically, we have classes like NodePtr/Ref/HashEqual.
After unified object protocol, these names are just alias of the object counterpart.
Moreover, there are helper macros defined over the places for defining these object.

This PR consoldiate the terminologies into the corresponding ones
in the Object system so we have a clean and consistent API moving forward.

* Update include/tvm/attrs.h

Co-Authored-By: Wei Chen <ipondering.weic@gmail.com>

* fix compilation

Co-authored-by: Wei Chen <ipondering.weic@gmail.com>

[Relay][VM][Interpreter] Enable first-class constructors in VM and interpreter via eta expansion (#4218)

* Fix constructor pretty printing

* Make Module::HasDef name consistent with API

* Add VM constructor compilation via eta expansion

* Lint

* Fix CI

* Fix failing test

* Address comment

* Retrigger CI

* Retrigger CI

* [NODE][REFACTOR] Refactor reflection system in node.

- Removed the old Node, Node is now just an alias of runtime::Object
- Introduce ReflectionVTable, a new columnar dispatcher to support reflection
  - This allows us to remove vtable from most node objects
  - The VisitAttrs are registered via TVM_RESGITER_NODE_TYPE,
    they are no longer virtual.
- Consolidated serialization and reflection features into node.

* Explicit type qualification when calling destructor.

* Fix SPIRV, more comments

* [REFACTOR][NODE][RUNTIME] Move Node to the new Object protocol.

This PR removes the original node system, and make node as a subclass of Object.
This is a major refactor towards a better unified runtime object system.

List of changes in the refactor:

- We now hide data_ field, use Downcast explicitly to get a sub-class object.
- Removed the node system FFI in python.
- Removed the node C API, instead use PackedFunc for list and get attrs.
- Change relay::Op::set_attr_type_key(attr_key_name) to relay::Op::set_attr_type<AttrType>().
  - This change was necessary because of the new Object registration mechanism.
  - Subsequent changes to the op registrations
  - The change revealed a few previous problems that is now fixed.
- Patched up a few missing node type registration.
  - Now we will raise an error if we register object that is not registered.
- The original node.h and container.h are kept in the same location.
- Calling convention: kObjectHandle now equals the old kNodeHandle, kNodeHandle is removed.
- IRFunctor now dispatches on ObjectRef.
- Update to the new type checking API: is_type, derived_from are replaced by IsInstance.
- Removed .hash member function, instead use C++ convention hasher functors.

* Address review comments

* Add EtaExpand to transform API

* Add test case

* Implement the virtual machine

Co-Authored-By: wweic <ipondering.weic@gmail.com>

* Fix rebase build issues

* Reorganize vm.py and fix allocator bug

* Remove compiler

* Remove tests

* Remove backend/vm/vm.cc too

* Fix docs

* Fix doc

* Fix doc

* Add vm docs

* Remove change to dead_code.cc

* Remove Relay logging

* Remove reduce

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Reformat

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Address feedback

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Apply suggestions from code review

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Fix a couple outstanding comments

* Last couple comments

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Address code review feedback

* Fix final comment

* Address comments

* Error reporting and example

* add Const

* Explicitly delete copy assignment operator

* Fix rebase

* Pass 3rd arg to fusion