Split service acceptance test modules

[yvette-carlisle]

Summary

• split docs extension acceptance helpers into a child module
• split knowledge page acceptance fixtures into a child module
• split trace admin observability fixtures into a child module

Validation

• RUSTC=/run/current-system/sw/bin/rustc cargo make fmt-rust && RUSTC=/run/current-system/sw/bin/rustc cargo make check after docs segment
• RUSTC=/run/current-system/sw/bin/rustc cargo make fmt-rust && RUSTC=/run/current-system/sw/bin/rustc cargo make check after knowledge segment
• RUSTC=/run/current-system/sw/bin/rustc cargo make fmt-rust && RUSTC=/run/current-system/sw/bin/rustc cargo make check after trace segment