feat: function that generates partition rules

[sunng87]

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Refer to a related PR or issue link (optional)

#6591

What's changed and what's your intention?

This patch adds a function that can generate partition rule expression based on given:

1. all possible characters of the string
2. max length of the string
3. how many partitions to have
4. provided hardstops

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.