[SLP] Use BatchAA to reduce capture analysis cost [NFC]

SLP makes very heavy use of aliasing queries to construct pointer dependencies for scheduling purposes.  AA internally usings pointerMayBeCaptured to prove some noalias results.  In a local profile, we were spending about 4% of total O2 time in capture tracking.  By using BatchAA interface - which caches capture results - this drops to 2%.

Note that there is no invalidation of BatchAA here.  This assumes that no transformation done by SLP invalidates alias or capture results.  This is the same assumption made by the existing AliasCache, so this is not a new assumption in the code.