implementation of full declustering, SLtrigger interface, and synchronisation of candidate muon fill

This MR significantly updates the SLtrigger entity, and fixes its interface with other entities:

• move from hardcoded types for eta and phi strip data (e.g. array_10x128b) to those defined in trigalgopkg.vhd (e.g. t_PHISTRIP_BI)
• changed signatures of the first declustering helper function to take a 7-bit vector (instead of 7 logic signals) as an input
• partially merge trivial and ordinary parts of the two declustering steps, so that generation is dealt with correctly by simulation
• implement the complete function for the second declustering step
• synchronise signals which compose the output candidate
• implement separate entities for retrieval on each layer of the hit which is closest to the candidate, and for the filling of the candidate word

Results:

In order not to violate timing requirements, a few delays have been introduced - mostly in the part which determines the closest hit to the candidate muon on each layer.

Tagging @fmorodei and @vari