HAT Package API fixes
`HATFile.functions.link_target` was being incorrectly composed atter initialization
Added some well-defined keys that are going to be of use with ONNX integration
- Doesn't support full HAT target information yet
- Adds pathway to specify function auxiliary information in
PackageBuilder
- Adds simple ONNXHATPackage that can parse a HAT package for functions
with ONNX auxiliary metadata
Initial implementation of package metadata. Two options are considered:
1. A free-standing [custom_metadata] table with the user-defined fields
```
[custom_metadata]
Dependencies = ["numpy", "onnx", "scipy"]
Documentation = "https://docs.readthedocs.io."
SHA = "0bb913ce84afa28127ea3fd2a9995e219dad322a"
"Release Notes" = "https://stackoverflow.com"
```
2. Attaching the custom metadata as part of the [description] table. [Current implementation]
```
[description]
...
[description.auxiliary]
Dependencies = ["numpy", "onnx", "scipy"]
Documentation = "https://docs.readthedocs.io."
SHA = "0bb913ce84afa28127ea3fd2a9995e219dad322a"
"Release Notes" = "https://stackoverflow.com"
```
Also support updating license_url/author/version fields as well-known metadata.
HAT schema PR: https://github.com/microsoft/hat/pull/7
Related work items: #3239
HAT Package API fixes
`HATFile.functions.link_target` was being incorrectly composed atter initialization
Added some well-defined keys that are going to be of use with ONNX integration
- Doesn't support full HAT target information yet
- Adds pathway to specify function auxiliary information in
PackageBuilder
- Adds simple ONNXHATPackage that can parse a HAT package for functions
with ONNX auxiliary metadata