[dalehamel]

Summary

Adds a generic, runtime-configured foundation for PID-scoped userspace probes.

• observes process/mapping lifecycle asynchronously without blocking PID-event processing
• resolves runtime-supplied ELF symbols or build-ID-scoped file offsets
• opens mapped objects through namespace-correct, inode/device-verified paths
• attaches paired PID-scoped uprobes/uretprobes with bounded link ownership
• reconciles links across late mappings, unmaps, exec, PID reuse, exit, and shutdown
• exports attachment/reconciliation counters and active-process/link gauges

This change intentionally contains no Yugabyte-, lock-, or pthread-specific symbol knowledge. Lock-wait and lock-held state machines will consume this substrate in follow-up PRs.

Lifecycle and compatibility

• sched_process_exec invalidates the exact per-PID mapping marker before userspace synchronization.
• Process identity combines executable identity, start time, address-space data, and an explicit exec generation, including same-image exec.
• Observer callbacks are asynchronous, PID-coalesced, panic-isolated, and bounded by observed PIDs.
• Return probes attach before entry probes; cleanup closes entry links before return links.
• Partial target attachment retries only unresolved offsets.
• Descriptor validation bounds links, points, and build-ID input before ELF or kernel work.
• Uses ordinary PID-scoped links; no attach cookies or uprobe_multi requirement (Linux 5.10 compatible).
• Mapping refresh remains event-driven; this does not add periodic process scans or a dynamic-loader hook.

Stack

• Base: [I/O profiles 1/4] Add synchronous I/O latency probes #53 (dale/io-network-probes-sync)
• This is a sibling of [I/O profiles 2/4] Add async correlation and io_uring latency #54-[I/O profiles 4/4] Add TCP sequence latency profiles #56; those PRs remain independent.
• Planned follow-ups: generic lock-wait profiling, then bounded lock-held profiling.

Validation

• make generate
• make -C support/ebpf lint
• targeted unit tests for metrics, process access, process manager, tracer, and userspace targets
• race tests for process manager, tracer, and userspace targets
• go vet on changed packages
• repository golangci-lint on changed package trees: 0 issues
• privileged real-kernel PID-scoped uprobe/uretprobe integration test (5 repeated runs during development)
• rebuilt amd64 and arm64 embedded eBPF objects
• git diff --check

Full go test ./... is not runnable in the local container because unrelated suites require nested/rootless Docker and generated test fixtures. The directly changed packages and their race suites pass.