[FEA] Add nested struct support in serial hash functions

[rwlee]

Is your feature request related to a problem? Please describe.
Supported nested structs in serial mumur3 and md5 hash functions.

Describe the solution you'd like
Add flattening with struct null pushdown in top level hash functions. Should be straightforward with proper flattening utilities.

Describe alternatives you've considered
Adding struct support as part of the type dispatch, but this approach would require recursion for nested structs. Flattening within that dispatch would also cause issues because the struct parent null pushdown would have to be done per row.

[github-actions]

This issue has been labeled inactive-30d due to no recent activity in the past 30 days. Please close this issue if no further response or action is needed. Otherwise, please respond with a comment indicating any updates or changes to the original issue and/or confirm this issue still needs to be addressed. This issue will be labeled inactive-90d if there is no activity in the next 60 days.

[github-actions]

This issue has been labeled inactive-90d due to no recent activity in the past 90 days. Please close this issue if no further response or action is needed. Otherwise, please respond with a comment indicating any updates or changes to the original issue and/or confirm this issue still needs to be addressed.

[GregoryKimball]

I believe this is closed by #11292, please feel free to reopen with an update.