Port partiql-lang-kotlin signatures to partiql-plan

[RCHowell]

Relevant Issues

• https://github.com/orgs/partiql/discussions/64
• Generates a partiql prelude for PLK partiql-lang-kotlin#1490

Description

• What? — It dumps the existing (0.14) routines (ops/functions/aggregations) to a definitions file a’la substrait extensions.
• Why? — We have to redefine all of the functions on PType now, so this is our indirection (which partiql-lang-rust may leverage)

This commit writes the current function signatures and variants to Ion files (like substrait extensions) so that PartiQL function signatures can be expressed independently of implementations. I am using these for my PR which moves functions out of SPI and into planner/eval respectively.

Open Questions

• What might be some limitations of this representation?
• Are the types sane for defining inputs/outputs?
• How might packaging/namespacing fit into this? i.e. why even have sql99::… and partiql::… namespaces?
• Is there value in these being public and consumed across PartiQL implementations, or is it just a nice-to-have for plk developers.
• Where might these live long term if shared?
• How are signatures stringified (specific/key) for representing in a plan?

License Information

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.