Feat add pivot transform to mo.UI.dataframe #7345 (#7584)

## 📝 Summary

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If this PR fixes any issues, list them here by number (e.g., Fixes
#123).
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Fixes #7345

## 🔍 Description of Changes

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problem addressed and how it was resolved. If applicable, provide before
and after comparisons, screenshots, or any relevant details to help
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### Backend

- Created handler and types for `PivotTransform` in
`marimo/_plugins/ui/_impl/dataframes/transforms`
- Ibis backend doesn't support pivot. The handler implementation is
using group_by.

### Frontend

- Added icon to mo.ui.dataframe transform panel.
- Added `PivotTransformSchema` with `column_ids, index_column_ids,
value_column_ids, aggregation` parameters in
`frontend/src/plugins/impl/data-frames/schema.ts`.
- ~~Added effect to collect unique column values so new column names can
be generated on the frontend.
`frontend/src/plugins/impl/data-frames/panel.ts`~~

## 📋 Checklist

- [x] I have read the [contributor
guidelines](https://github.com/marimo-team/marimo/blob/main/CONTRIBUTING.md).
- [x] For large changes, or changes that affect the public API: this
change was discussed or approved through an issue, on
[Discord](https://marimo.io/discord?ref=pr), or the community
[discussions](https://github.com/marimo-team/marimo/discussions) (Please
provide a link if applicable).
- [x] I have added tests for the changes made.
- [x] I have run the code and verified that it works as expected.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: heizerbalazs

docs/api/inputs/dataframe.md

@@ -20,6 +20,8 @@ Supported transforms are:
 - Shuffle Rows
 - Explode Columns
 - Expand Dict
+- Unique
+- Pivot
 
 !!! info "Request a Transform"