feat: add opt-in sleepable uprobes

[swananan]

Summary

• add opt-in [ebpf].sleepable_uprobe configuration and --sleepable-uprobe, both disabled by default
• probe the required sleepable helper path, use RingBuf-only output, and reject the PerfEventArray conflict early
• probe sleepable tail-call support and safely limit deep DWARF backtraces to the inline depth when unavailable
• document the behavior, limitations, and Aya follow-up

Validation

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test -p ghostscope-loader kernel_caps::tests
• standard e2e runner job e83885a8a471: test_sleepable_uprobe_backtrace_uses_a_kernel_supported_depth