Move the palette Randomize colors to the edit palette panel and remove the color previews from the edit palette button labeling

[afercia]

Description

Splitting this out from #65124
Please refer to the conversation on that PR and issue.

• The 'Edit palette' button uses an unique, inconsistent, design as the visual labeling includes some 'color previews'. This is inconsistent and confusing.
• The colors preview are supposed to change when clicking the 'Randomize colors' button below them. However, this doesn't work for all themes. For example with Twenty Twenty-Four no changes are shown at all. The previews are aribtrarily limited to the first 5 colors provided by the theme. Depending on the color, the randomization may not genereate any change (or may generate barely visible changes).
• The 'Randomize colors' button should be better placed one level deeper into the edit palette panel, where the entire color palette is shown. This way, randomized colors will eb shown for the entire palette.

In the animated GIFs below, with Twenty Twenty-Four or any other theme with the first 5 colors that aren't changed by the randomization:

• Current: No change is shown.
• Proposed: Randomizaiton moved to the edit palette panel, where the entire palette is shown and not arbitrarilu limited to the first 5 colors.

Current	Proposed

Step-by-step reproduction instructions

• Set Twenty Twenty-Four as active theme.
• Go to Site editor > Styles > Colors
• Observe the 'Palette' section.
• Observe the colors preview are places inside the 'edit palette' button, which is an unique and inconsistent pattern.
• Observe that clicking the 'Randommie colors' button doesn't show any change in the colors preview.

Screenshots, screen recording, code snippet

No response

Environment info

No response

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes

[afercia]

Noting that the PR #65619 which is the first step to move the Styles panel to the navigation 'black' panel (see #66376) makes the color previews (the 'swatches') in the edit palette button even more confusing. I'd argue they would be pretty pointless as the default view on the iframe shows the Style Book with the full palette.

As mentioned eearlier, the swatches in the button aren't functional with some themes because they are arbitrarily limited to the first 5 colors of the palette. Clicking the Randomizer button may not show any change in the swatches but it would show changes in the Style Book. To me, this is one more good reason to remove the swatches and move the randomizer one level deeper.

@cc @jameskoster @jorgefilipecosta

Screenshot from #65619 with Twenty Twenty-Four set as active theme.