Move more code out of unicode-table-generator into core

[clarfonthey]

Extension to #147622 which further reduces the size of the generated code, moving more of it into libcore directly.

This way, the verification code and the unsafe methods are right next to each other can be more easily understood.

Doesn't actually affect the compiled data, just moves around the code.

[rustbot]

library/core/src/unicode/unicode_data.rs is generated by the src/tools/unicode-table-generator tool.

If you want to modify unicode_data.rs, please modify the tool then regenerate the library source file via ./x run src/tools/unicode-table-generator instead of editing unicode_data.rs manually.

[rustbot]

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