DEBUG-2334 repair instrumentation of virtual and later-defined methods

[p-datadog]

What does this PR do?

This PR changes DI instrumentation to not fail if the current definition of a method is not available, when installing method probes.

Motivation:
DI instrumentation code assumed it was able to obtain the current definition of the target method for method probes. This is not correct when 1) class is defined but the target method is not (perhaps because the method would be defined later), and 2) when the method is virtual and handled by method_missing.

Change log entry
None

Additional Notes:

For virtual and later-defined methods, the stack trace reported to backend currently would not include the method itself (since we don't have its definition to get its location from). Later if/when begin/end trace points are added to method instrumentation we should be able to obtain the actual method location at probe invocation time and fill in the top stack frame then.

How to test the change?

Unit tests are included

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-11-13 20:26:10

Comparing candidate commit 311198d in PR branch di-virtual with baseline commit 34d1947 in branch master.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 28 metrics, 2 unstable metrics.

scenario:method instrumentation

• 🟥 throughput [-25778.973op/s; -24695.177op/s] or [-11.391%; -10.913%]