[18.0][ADD] otel

[ryanc-me]

This is still very WIP.

Things to do:

• Cron tracing
• Add span/trace IDs to logs (https://opentelemetry-python-contrib.readthedocs.io/en/latest/instrumentation/logging/logging.html)
• Support for logging to an OTel collector?
• Add optional odoo.http-level tracing (i.e., all requests), with docs on sampling to extract wanted info
• Allow enable/disable tracing per level (RPC, ORM, Cron, DB). For each type, a few options:
  • Allowlist for methods (empty for all)
  • Allow excluding particular models (ir.model.access, etc)
  • Allow excluding model:method pairs?
  • Only trace when parent is tracing (possible for DB?)
• PII handling
• Tidy up bootstrap code (metrics/logs not required?)

The work is split into a few modules:

• otel is the base OpenTelemetry integration, Python-only (i.e., traces from the Odoo backend)
• otel_web adds support for tracing from the client-side. Split into a separate module so migrations are easier (JS-heavy modules tend to take longer to be migrated)