Move ascii, bit_length, btrim, chr to datafusion-functions

[PsiACE]

Is your feature request related to a problem or challenge?

As part of #9285 the ascii, bit_length, btrim, chr string functions should be migrated to the new datafusion-functions crate in the new structure

Describe the solution you'd like

This is the follow-up work of #9533, but I think we can also refer to the migration of other functions, such as #9286 & #9216.

Describe alternatives you've considered

No response

Additional context

No response

[PsiACE]

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