Update cache configuration terminology from “lines” to “sets”

[dangfan]

Summary

This PR aligns Ripes cache terminology with standard cache organization vocabulary by renaming configuration and documentation references that previously used “lines” where “sets” is the precise term (especially for set-associative caches). It also makes the “Words/Line” label clearer by changing it to “Words per Line”.

References

1. Wikipedia – Cache placement policies
   Defines set-associative cache as a cache “divided into n sets and each set contains m cache lines” and explains that the set is determined by the index bits in the address.
   https://en.wikipedia.org/wiki/Cache_placement_policies

2. Wikipedia – CPU cache
   Explains cache associativity, including N-way set-associative caches where each memory location may be cached in N locations, and describes how the memory address is split into tag, index, and block offset, with the index specifying the cache set.
   https://en.wikipedia.org/wiki/CPU_cache

3. ScienceDirect Topics – Set-Associative Cache
   An authoritative engineering reference stating that a set-associative cache is organized as an array of sets (each set containing multiple cache lines/ways) and that the set index selects the set, with tag and block offset used to identify the specific line and word.
   https://www.sciencedirect.com/topics/computer-science/set-associative-cache

4. UCSD CSE141 Cache Handout (university teaching material)
   Defines cache terminology including cache set (a row in the cache indexed by the set index bits) and explains the address decomposition into offset, set index, and tag used to locate data in a set.
   https://cseweb.ucsd.edu/classes/su07/cse141/cache-handout.pdf