Annotate arkouda build time deltas (#29107)

[reviewed by @benharsh]

This annotates a recent downtick and uptick we saw in build times when
switching to LLVM 22, which wasn't supported by Chapel 2.8, requiring
Arkouda-release perf testing to use the bundled version which happens to
be built with better optimization levels and therefore runs faster,
reducing compile times. Once Arkouda release testing was updated to 2.9,
the system LLVM was used again (albeit version 22 rather than the
previous 21), largely restoring the previous times.

Author: bradcray

test/ANNOTATIONS.yaml

@@ -2735,6 +2735,10 @@ arkouda: &arkouda-base
     - Fix performance regressions from divide-by-zero check (Bears-R-Us/arkouda#5416)
   04/19/26:
     - Make the loop iterating over multiple parquet files parallel (Bears-R-Us/arkouda#5486)
+  05/15/26:
+    - Switched system LLVM to 22 requiring Arkouda-release to use CHPL_LLVM=bundled which runs faster due to better -O levels (#28821)
+  06/30/26:
+    - Updated Arkouda release to Chapel 2.9 permitting the use of CHPL_LLVM=system again now using LLVM 22 (#29033)
 
 arkouda-string:
   <<: *arkouda-base