XDP declarations are moved from ebpf_nethooks.h.

[shpalani]

Description

This PR contains:

1. New file net_ebpf_xdp_hooks.h containing XDP headers and hooks.
2. XDP headers and hooks removed in ebpf_nethooks.h.
3. Docs changed to reflect the change.
4. Test samples to include the new header file.

Additional details:

• Remove support for the netebpfext's XDP hook in ebpf-for-windows #2974 moved XDP functionality to XDP_TEST in netebpfext. The second part involves removing XDP_TEST and its dependencies from ebpf-for-windows so that the xdp-for-windows extension can have its ebpf header and tests. This PR targets a temporary move of XDP headers and hooks until the dependent XDP_TEST imprints are removed in ebpf-for-windows. This helps xdp-for-windows extension (XDP must define its eBPF structs and helpers itself #613) to package a nupkg.
• Also, this can be a breaking change for existing XDP_TEST external consumers. Hence, targeted v0.19.0.

Testing

_Do any existing tests cover this change? Yes
Are new tests needed? No

Documentation

_Is there any documentation impact for this change? Yes

Installation

_Is there any installer impact for this change? No.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 8 lines in your changes missing coverage. Please review.

Project coverage is 86.57%. Comparing base (d7c7af6) to head (cb3606e).
Report is 270 commits behind head on main.

Files	Patch %	Lines
tests/end_to_end/helpers.h	12.50%	7 Missing ⚠️
netebpfext/net_ebpf_ext_xdp.c	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3793      +/-   ##
==========================================
+ Coverage   83.78%   86.57%   +2.78%     
==========================================
  Files         143      153      +10     
  Lines       27297    28802    +1505     
==========================================
+ Hits        22870    24934    +2064     
+ Misses       4427     3868     -559     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.