network-boot: include Nightly DTS entry checks in iPXE menu tests

[yuliuyi717-ux]

What

• update PXE002.001 menu-order assertions to include Dasharo Tools Suite (Nightly)
• shift OS installation and iPXE Shell index checks accordingly
• add PXE004.002 to verify the Nightly DTS menu option boots to DTS and presents expected options

Why

Dasharo/dasharo-blobs now adds a Nightly DTS iPXE entry for Dasharo/dasharo-issues#1041.
OSFV needs to validate the new menu layout and option behavior.

Related

• dasharo: add Nightly DTS entry to iPXE network menu dasharo-blobs#54
• Add "Dasharo Tools Suite (Nightly)" to iPXE menu entry dasharo-issues#1041

[yuliuyi717-ux]

Validation note for reviewers:

This PR covers the OSFV portion of Dasharo/dasharo-issues#1041.

What is validated here:

• the iPXE menu-order assertions are updated to include Dasharo Tools Suite (Nightly)
• the downstream index expectations are shifted accordingly
• a dedicated PXE004.002 path is added so the Nightly DTS menu option is exercised explicitly in OSFV

So this PR is intended to verify both the new menu layout and the Nightly-entry boot path expected by the issue, while the actual menu entry itself is introduced in Dasharo/dasharo-blobs#54.