ElasticSearch Unified Index

Tracking creating a unified template for Elasticsearch indices, with proper datatypes and defaults for each of our fields. Essentially the question that we want to answer here is: how do we transform a ``BenchmarkResult`` dataclass into JSON?

Start by locating the BenchmarkResult dataclass and the code that sends benchmark results to Elasticsearch. Define how each field should be represented in JSON, including datatypes and defaults, then determine how that mapping should produce one unified Elasticsearch index template. Done means the template and serialization behavior consistently cover all BenchmarkResult fields.

Written by the indexing model from the issue text.