Add radio options to ensure that gamma and palette are not set at the…

… same time (#2044)

* Add layer loading spinner and remove layer button

* Add observe method to FakeEeTileLayer

* Add observe method to FakeGeoJSONLayer

* Add remove layer confirmation

* Add spinner event for removing layer

* Add support for removing non-ee layers

* Update layer remove widget

* Minor style tweaks.

* Add radio buttons for palette and gamma settings

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

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Co-authored-by: Qiusheng Wu <[email protected]>
Co-authored-by: Nathaniel Schmitz <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>