Add new bpftrace section for DTrace document

[egmc]

This PR adds new section which explains how to use DTrace with bpdtrace command, related to my previous PR #4456 .

Since this PR adds completely new section, I want to explain why it should be added, why it is useful for PHP users. Hoping it could be merged.

Background / Motivation

To encourage PHP users to use useful, stable DTrace based tracepoints easier way.

DTrace is basically an option, though most of PHP packages provided by Linux distributions(aside from Debian) are enabled in reality.

Ubuntu 24.04 Noble is also disabled because of build error from upstream, though enabled again from next version. Here are related issues:

• https://bugs.launchpad.net/ubuntu/+source/php8.3/+bug/2088977
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1110885

Although the existing SystemTap section requires users to install SystemTap which is a bit difficult on modern Linux distributions.

For instance, I have installed SytemTap( And gcc-12 because of the missing dependency) with Ubuntu 22.04 Jammy. I got bunch of errors like below.

Systemtap version 4.6/0.186
https://gist.github.com/egmc/1667b12fcf58eb4fdfbddce256f35084

It may be fixed, though it could be hard for users who tried the functionality for first time.

In contrast, eBPF is now supported natively in mainline Linux kernels, and bpftrace (a high-level eBPF tracing frontend) is available as a standard package on
major distributions (Fedora, RHEL, Oracle Linux, Debian, Ubuntu). The examples in the new section work reliably out of the box with a simple package install,
making them a more practical starting point for users who want to trace PHP on Linux.

bpftrace v0.21.2
https://gist.github.com/egmc/467678a1b6b845bd0a5605dcf3aaa906

So adding bpftrace version would provide more straightforward, easy way to uses.

Notes

• The new section is placed after the existing SystemTap section
• Probe names and arguments match the existing DTrace/SystemTap documentation
• The all_probes.bt script mirrors the existing all_probes.stp example for consistency

[lacatoire]

Nit: indentation inside the new <sect1 xml:id="features.dtrace.bpftrace"> uses mixed levels (1/4/6 spaces) whereas the rest of the file uses a regular 1/2/3 hierarchy, matching the SystemTap <sect1> above. Could you realign to match? For example <title> at 2 spaces, <sect2> at 2, <para> inside at 3.

[egmc]

@lacatoire Thank you for the quick comment! I'll add commits as suggested and fix indent levels as well.

[egmc]

@lacatoire I think I've fixed it up to this point. Should I push everything back using sqush?

[lacatoire]

@egmc simple push, no squash

[egmc]

The issues pointed out have been addressed, and I have completed the local build verification.

If any further corrections or explanations regarding the background are needed, I would happy to do it.
Thanks.

[jordikroon]

Just a few para's that should be simpara as well (because they only contain parsed text).

[egmc]

@jordikroon Certainly. I've incorporated your suggestions and checked the rendering again; it looks good.Thanks!