spike: improve type perf

[noahbald]

Description

This PR is an attempt to investigate improvements to performance by trimming large types.

Motivation and Context

Large types presumably negatively affect the binary size and performance of the application. There are some large types discovered by the usage of top-type-sizes

• Attr due to it's use of AttrId in unknown variants, can be improved by Box-ing
• Jobs due to having many members, can be improved by using Vec of dyn values

How Has This Been Tested?

• Binary size has been tested by making a release build and inspecting the binary's size
• Runtime performance has been tested against w3c and oxygen suites.

It seems that these changes has virtually no effect on runtime performance and the gains in binary size are marginal, going from 19.6MB -> 19.7MB

Types of changes

Fixes

Features

Breaking changes

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.