Add and configure OpenTelemetry for tracing

This will auto-hook into Rails and other libraries to produce traces.

No explicit trace spans are created yet, only automatic instrumentation.

The only explicit configuration is to avoid tracing the /up endpoint
used for health checks. This prevents a large number of unhelpful traces
from being created. All other configuration is provided through
environment variables, specified in `forms-deploy`.

We also disable logging for Rake tasks to avoid cluttering output
when running tasks like database migrations.

Finally, OpenTelemetry is only enabled if the `ENABLE_OTEL` environment
variable is set to "true". This allows us to control whether tracing
is active without changing the code. Again, this is configured in
`forms-deploy` when deploying to different environments.

Author: whi-tw

Gemfile

@@ -123,3 +123,9 @@ group :test do
   # For validating against the JSON schema for form submissions
   gem "json_schemer"
 end
+
+gem "opentelemetry-sdk", "~> 1.10"
+gem "opentelemetry-instrumentation-all", "~> 0.89.1"
+
+gem "opentelemetry-exporter-otlp", "~> 0.31.1"
+gem "opentelemetry-propagator-xray", "~> 0.26.0"

Gemfile.lock

@@ -1043,4 +1043,4 @@ RUBY VERSION
    ruby 3.4.8p72
 
 BUNDLED WITH
-   2.7.1
+   2.6.9