Simplify LRT/VSI trigger step construction

FYI @jmasik, follow-up to !66875 (merged).

The FS LRT CA configuration was too deeply nested, and in particular had SelectionCA containing SelectionCA, resulting in odd placement of the VSI hypo alg. This simplifies the structure such that:

• CommonConfiguration.getCommonInDetFullScanLRTCfg produces a plain CA holding the FS FTF and LRT algs
• VrtSecInclusiveConfiguration.VrtSecInclusiveMenuSequence and FSLRTTriggerCfg.FullScanLRTMenuSequence produce a MenuSequenceCA directly, scheduling the reco & hypo in a single function.

This way we are able to reenable the fsvsi triggers in the CA menu as well.

There were some weird naming conventions (VSIger etc) arising from some name sanitisation in the CF (@fpastore probably knows about this): https://gitlab.cern.ch/atlas/athena/-/blob/main/Trigger/TriggerCommon/TriggerMenuMT/python/HLT/Config/ControlFlow/MenuComponentsNaming.py#L25 So, I removed the unnecessary Trigger and Cfg substrings from the step names.

Continues ATR-26732

May need to verify that chain counts are sensible.