Eliminate tuple allocations in seekReadCustomAttributeRow via a custom reader for attribute rows (#9218)
Eliminate tuple allocations in seekReadCustomAttributeRow via a custom reader for attribute rows (#9218)

* seekReadCustomAttributeRow as a struct 3-tuple

* Read custom attributes via a specialized reader
dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp