fix: stream group topn used wrong types for hash key

[xxchan]

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What's changed and what's your intention?

fix #7276

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

[codecov]

Codecov Report

Merging #7326 (3421b21) into main (21775bc) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #7326   +/-   ##
=======================================
  Coverage   73.05%   73.05%           
=======================================
  Files        1069     1069           
  Lines      170996   170999    +3     
=======================================
+ Hits       124918   124922    +4     
+ Misses      46078    46077    -1     

Flag	Coverage Δ
rust	73.05% <0.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/stream/src/from_proto/group_top_n.rs	0.00% <0.00%> (ø)
src/storage/src/hummock/sstable/bloom.rs	96.59% <0.00%> (-2.28%)	⬇️
...rc/storage/hummock_sdk/src/filter_key_extractor.rs	92.32% <0.00%> (-0.26%)	⬇️
src/stream/src/executor/aggregation/minput.rs	96.49% <0.00%> (+0.10%)	⬆️
src/storage/src/hummock/compactor/mod.rs	83.63% <0.00%> (+0.15%)	⬆️
src/common/src/cache.rs	97.54% <0.00%> (+0.22%)	⬆️
src/batch/src/task/task_execution.rs	54.30% <0.00%> (+0.52%)	⬆️
src/meta/src/hummock/mock_hummock_meta_client.rs	66.31% <0.00%> (+0.52%)	⬆️

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[st1page]

rest LGTM