In declarative rewrite rules, a symbol can be bound to op arguments or
results in the source pattern, and it can be bound to op results in the
result pattern. This means given a symbol in the pattern, it can stands
for different things: op operand, op attribute, single op result,
op result pack. We need a better way to model this complexity so that
we can handle according to the specific kind a symbol corresponds to.
Created SymbolInfo class for maintaining the information regarding a
symbol. Also created a companion SymbolInfoMap class for a map of
such symbols, providing insertion and querying depending on use cases.
PiperOrigin-RevId: 262675515
ac68637ba9