This PR introduces more clear naming prefix for C API type codes
to avoid conflict with other packages.

We also removed TVMArray and TVMType to directly use DLTensor and DLDataType.

* [REFACTOR][IR] Unify IntImm and UIntImm

This PR unifies UIntImm and IntImm to simplify the codebase.
Unsigned integer constants will also be stored as IntImm.

For uint constant that does not fit into int64(rare case), we introduced
an intrinsic tvm_big_uint_imm to construct such intgers by its
lower and higher 32bits.

* [REFACTOR][IR] Remove UIntImm to use IntImm

* rename big->large

* [REFACTOR][IR] tvm::Expr -> PrimExpr(Primitive Expr)

As part of unified IR, we will need to unify relay::Expr
and the current tvm::Expr under the same base type.

From the techinical point of view. tvm::Expr is a "primitive"
expression that only contains POD types and handles and does
not do life-cycle management.

This PR renames Expr->PrimExpr to clarify that.
We will send a subsequent PR to introduce the base expr class.

* Remove legacy VarExpr and ExprHash/Equal

* [REFACTOR][IR] Variable -> VarNode

* [REFACTOR][IR] Add/Sub/Mul/Div -> AddNode/SubNode etc.

* [REFACTOR][IR] Min/Max/FloorDiv/FloorMod -> MinNode/MaxNode etc.

* [REFACTOR][IR] EQ/NE/LT/LE/GT/GE/Select -> EQNode/NENode etc.

* [REFACTOR][IR] Add Node suffix to Select/Call/Load/Ramp/Shuffle/Let

* [REFACTOR][IR] Add node suffix to IntImm/UIntImm/FloatImm/StringImm

* [REFACTOR][IR] Add Node suffix to Any, AttrStmt, AssertStmt

* [REFACTOR][IR] Add Node suffix to Store/Provide/Allocate/Free

* [REFACTOR][IR] Add Node suffix to ProducerConsumer

* Fix lint

* style updates, test fixes

* [REFACTOR][IR] Introduce SeqStmt to replace Block

ir::Block was used to represent a sequence of Stmts in the original low-level IR.
The nested ir::Block structure is not really friendly for recursive visits,
especially when the statements are unrolled.

This PR introduce a SeqStmt that directly stores a sequence of statements in an Array container.
The new SeqStmt will be used as a replacement of the original Block structure.

* [REFACTOR] Migrate use of Block to SeqStmt.

* [REFACTOR] Remove Block

* Add more comments per yizhi's comment

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.

dtype.h -> runtime/data_type.h

Changes:
- Rename all old reference of tvm::Type to DataType
- ExprNode.type -> ExprNode.dtype
- Expr.type() -> Expr.dtype()
- Change Expr related functions to expr_operator.
  - DataType::min() -> min_value(DataType)
  - DataType::max() -> max_value(DataType)
- Move type constructor Int, UInt, Float, Handle, Bool into DataType.
  - Int(bits) -> DataType::Int(bits)
  - UInt(bits) -> DataType::UInt(bits)

* [LINT] Improve the check tool to handle ASF copyright message.

* [LINT] Remove unnecessary copyright message as per ASF requirement.

* Fix codegen hybrid

* [LINT] Broaden license checks to include html, xml

* [LINT] Fix rest of the files

* Fix notice

* [LINT] Improve check file type error message

* Add `set_body_simple` to Registry, refactor a lot of code to use it

* Add more types to Relay PackedFuncs

* Add Registry::set_body_method to easily make Node methods into
PackedFuncs

* Add set_body_method, set_body_node_method; start typing api_lang

* Add some docs, remove unused script

* Fix mysterious linter problem

* Touch up api_ir.cc

* Fix some issues with TOPI argument counts

* Revert changes to topi.cc to avoid problems with optional arguments

* A little more cleanup

* Type more of the api _ functions

* Whitespace

* Finalize names and docs for new registry helpers

* Update docs

* [HEADER] ASF header dir=include

* [HEADER] ASF Header dir=src

* [HEADER] ASF Header -dir=python

* [HEADER] ASF header dir=topi

* [HEADER] ASF Header dir=nnvm

* [HEADER] ASF Header -dir=tutorials

* [HEADER] ASF Header dir=tests

* [HEADER] ASF Header -dir=docker

* fix whitespace

* [HEADER] ASF Header -dir=jvm

* [HEADER] ASF Header -dir=web

* [HEADER] ASF Header --dir=apps

* [HEADER] ASF Header --dir=vta

* [HEADER] ASF Header -dir=go

* temp

* [HEADER] ASF Header --dir=rust

* [HEADER] Add ASF Header --dir=cmake

* [HEADER] ASF Header --dir=docs

* [HEADER] Header for Jenkinsfile

* [HEADER] ASF Header to toml and md

* [HEADER] ASF Header to gradle

* Finalize rat cleanup

* Fix permission

* Fix java test

* temporary remove nnvm onnx test

* [PASS] Allow compact checking when strides is available

* remove assert compact

* [RUNTIME] Add workspace pool

* fix doc

* fix the free list

* avoid zero size

* [IR] Add body to AssertStmt

* fix lint

* [REFACTOR/PASS] Formalize argument bind and match util

* grammar

* [CODEGEN/PASS] Improve callpacked lowering, allow pass array callback.

* fix cython

* [RUNTIME] Refactor runtime to be DLPack compatible. Enable plugin of new runtime.

* fix mac compile

* ok

* [ARITH/VISITOR] Modular Analysis, ExprFunctor, StmtFunctor

* retrigger

* [IRFunctor] Migrated CodegenC

* [IRFUNCTOR] Migrate CodeGenLLVM

* [IRFunctor] Migrate canonical

* [IRFunctor] Migrate vectorize

* [IRFunctor] migrate CodeGenStackVM

* [LLVM] Initial support for codegen LLVM.

* Fix the naming issue of codegen

* [CODEGEN] CUDA/OPENCL pipeline complete

* Hide TVMType by str in frontend