NH-34752 Parse txn filters and calculate tracing mode

[tammy-baylis-swi]

This is more steps towards implementing transaction filtering:

1. Update update_transaction_filters in the Configurator to use existing helper OboeTracingMode.get_oboe_trace_mode to map filter's tracing to int for liboboe
2. Also more checks for valid filter's regex values
3. Adds calculate_tracing_mode used by sampler to apply per-request filter or "global" tracing_mode that can also be configured.

This only filters for span <kind>:<name> right now because http.* attributes generated by instrumentation libraries are not yet available to the sampler, but this is gradually being implemented in OTel #936.

Example basic config file JSON I'm using with Django A:

{
    "tracingMode": "enabled",
    "transactionSettings": [
        {
            "regex": "SERVER:another/",
            "tracing": "disabled"
        },
    ]
}

Next PRs:

• Add two-signal check OR support for third filter component, signal (see Slack thread) See NH-34752 Add construct_url for calculate_tracing_mode #137
• Add more unit tests
• Add web request filtering -- best tested when some OTel #936 updates are merged and released
• infodev/customer docs update

Please let me know if any questions/suggestions!

[raphael-theriault-swi]

Since you're already compiling the regex in here wouldn't it make sense to store the result in txn_filter so it doesn't have to get recompiled on every match

[tammy-baylis-swi]

Good idea! Changed in d28c040.

[raphael-theriault-swi]

Looks good !