Blazor WebAssembly perf: InitializeNewAttributeFrame should use culture-insensitive ordinal string comparison

[SteveSandersonMS]

This is part of #22432

RenderTreeDiffBuilder currently does a culture-sensitive match when checking if an attribute name starts with on. This was not intentional - there's no reason we shouldn't do this with a culture-invariant match. This trivial change gives a 2-3% gain on the PlainTable/ComplexTable benchmarks.