PHP Benchmarks

We have some PHP Benchmarks in our repository: https://github.com/open-telemetry/opentelemetry-php/tree/main/tests/Benchmark

We don't run these on any sort of regular cadence and keep the reports. We'd probably want to come up with some methodology to run these and capture the data. We don't have dedicated runners for this, but it's most likely a good idea to capture some data on this.

We should follow up with other SIGs to see what they tend to do for benchmarking their libraries.