Put single-def CSEs into SSA (#26986)
Put single-def CSEs into SSA (#26986)

If we create a single-def temp during SSE, add it into SSA so uses of the temp
can benefit from assertion prop and similar.

Follow-up from some work proposed for #21973.

krk/coreclr,cshung/coreclr,cshung/coreclr,krk/coreclr,krk/coreclr,cshung/coreclr,poizan42/coreclr,cshung/coreclr,krk/coreclr,cshung/coreclr,poizan42/coreclr,poizan42/coreclr,cshung/coreclr,poizan42/coreclr,krk/coreclr,krk/coreclr,poizan42/coreclr,poizan42/coreclr