HLTResultMTByteStreamCnv: Don't use FullEventAssembler and implement local cache instead

Stop using the hidden cache and the overcomplicated infrastructure of FullEventAssembler and instead:

• implement an explicit simple local cache
• create ROBFragments and append them to RawEventWrite (aka FullEventFragment) directly

A similar solution will be implemented for L1 results in !30902 (merged)

This merge request affects 1 package:

• Trigger/TrigSteer/TrigHLTResultByteStream

Adding @tamartin ,@rbielski as watchers

added Trigger master review-pending-level-1 labels

cc @wiedenma for information

CI Result SUCCESS (hash 469ba512)

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 1
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 10554]

Unrelated warning, approving.

Tadej (L2)

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 4bb9fcab

added sweep:ignore label

resolved all threads