Add `append_n` method to `FixedSizeBinaryDictionaryBuilder`

[albertlockett]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
I am writing some code that appends multiple of the same value to the FixedSizeDictinoaryBuilder

Describe the solution you'd like
In GenericByteDictionaryBuilder, we have a helpful method called append_n, which can save us multiple key lookups:

arrow-rs/arrow-array/src/builder/generic_bytes_dictionary_builder.rs

Lines 304 to 316 in 0737c61

	/// Append a value multiple times to the array.
	/// This is the same as `append` but allows to append the same value multiple times without doing multiple lookups.
	///
	/// Returns an error if the new index would overflow the key type.
	pub fn append_n(
	&mut self,
	value: impl AsRef<T::Native>,
	count: usize,
	) -> Result<K::Native, ArrowError> {
	let key = self.get_or_insert_key(value)?;
	self.keys_builder.append_value_n(key, count);
	Ok(key)
	}

I would like it if the FixedSizeDictinoaryBuilder had a similar method.

Describe alternatives you've considered

for _ in 0..count {
    builder.append_slice(val)?;
}

Additional context

[alamb]

label_issue.py automatically added labels {'arrow'} from #8498