Hand-picking the smallest index type that fits a particular generated
array started with commit 3ad159537e. This
was to reduce the size of the generated library.
Since then, the number of types using UniqueStorage has grown a ton,
creating a long list of types for which index types are manually picked.
When a new UCD/CLDR/TZDB is released, and the current index type no
longer fits the generated data, we fail to generate. Tracking down which
index caused the failure is a pretty annoying process.
Instead, we can just use size_t while in the generators themselves, then
automatically pick the size needed for the generated code.
b2164ad979