Tracking issue: Enhance Alloy syntax to support more pipeline use cases

[rfratto]

While the Alloy syntax is powerful, it lacks some capabilities:

• No support for conditionals in Alloy expressions
• Lacking a fleshed out set of standard functions
• Lacking support for configuring Alloy with YAML
• Lacking support for using Alloy expressions to transform and route data

Users are forced to identify workarounds for these features, but a workaround doesn't always exist.

A series of proposals should be introduced to gradually solve these issues.