[TextField] Implement variant without shrinking label

This isn't standard Material UI, but the spec's handling of input labels is perhaps one of its most loved and hated bits. Labels outside is a pretty common pattern, so would be nice to just have a variant for it, to avoid losing the convenience of the high-level TextField, etc abstraction

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Summary 💡

Basically something like <TextField variant="normal"/> would render

<FormControl ..>
   <InputLabel> ...  // perhaps a bit larger/bolder than the MUI default, no shrink
   <OutlinedInput> ..
   <FormHelperText>..
   ...   

Basically something sort of like the bootstrap input styling example

Motivation 🔦

Ease of use for a non-spec, but common pattern for fields and their input labels