Data Explorer: Add support for formatting options (#382)

* Move format_column to it's own file

* Move to an R implementation for formatting

* Adapt tests for new defaults

* Add an R implementation matching Python tests

* Move to own formatter

* Support format options for the summary panel + refactor

* typo

* Some small improvements

* Improve comments in the `apply_thousands_separator` function

* Apply suggestions from code review

Co-authored-by: Lionel Henry <[email protected]>

* `format_vec` -> `format_list`

* Improve comments for `format_object`

* Improve list formatting logic

* Move vectors constructors closer to type checks

* Use a global fallback format string.

* Don't clone as it's not needed.

* Expose a more generic version and move assumptions closer to the R function call.

* Use `harp::list_get()`

* Use if/else instead

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Co-authored-by: Lionel Henry <[email protected]>

Author: dfalbel