ATLASRECTS-5750: Lwtnn maps
Accessing LWTNN via a string-keyed map is taking too long. Implementation of speed-ups.
Picking up faster methods made available in !38021 (merged) (Tweaks introduced in !38033 (merged) have been pulled into the MR already)
Note: Changes to function calls used in SiClusterOnTrackTool. Need to akkpkg for testing