After this commit, every non-key field is treated as if it was optional
while every key field (plus every auto-generated `Kind` field) - as if
it was required.
This allows to avoid having to specify the `rootType` (stable within
the entire tree) manually each time a reference is introduced.
Thanks to that, a much nicer syntax of:
```yaml
- name: MyTypeField
reference-to: TypeDefinition
```
can replace the current one:
```yaml
- name: MyTypeField
reference:
pointeeType: TypeDefinition
rootType: Binary
```
Currently, using `std::vector` in these breaks invalidation, so to
avoid potential confusion, we shouldn't use it in docs either.
Note that it's fine to use `std::vector` in non-invalidation-enabled
TTG instances.
This commit switches `model::Type::ID` from being a GUID to be a
progressive number, in order to make things easier for humans.
On top of this, this commit introduces the following changes:
* TypeCopier: import all the necessary PrimitiveTypes and improve
handling of CustomName.
* Move Kind as the last field of the key of each TupleTree type used in
an `UpcastablePointer`.
* Update the ground truth of tests to ignore the `CustomName` in favor
of focusing on `OriginalName`.
* Increase adoption of `model::Binary::makeType`, equivalent to
`Binary.recordNewType(makeType<model::*Type>())`.
The control-flow graph and all its hierarchy components
have been moved from `model` to `efa`. The CFG is now
serialized onto the LLVM IR module as a metadata.
Model classes are now described by a YAML document, which is used to
generate C++ headers containing classes and all the boilerplate
required for YAML serialization/deserialization, usage in
SortedVectors, etc. See the README in include/revng/Model for more
info.
Ivan Krysak