[Panel] Add `-space` css properties for `header-content` slot

[macandcheese]

Check existing issues

• [X] I have checked for existing issues to avoid duplicates

Description

It is common to slot rich content into the header-content slot of a Panel. Currently, they have baked-in padding that isn't always desirable - where slotted items are intended to be full-height.

I'd like to have the ability to remove this with a calcite-panel-header-content-space (or similarly named) css property.

Acceptance Criteria

I have the ability to control the padding of the slots mentioned above.

Example Use Case

Priority impact

p4 - not time sensitive

Calcite package

• [X] @esri/calcite-components
• [ ] @esri/calcite-components-angular
• [ ] @esri/calcite-components-react
• [ ] @esri/calcite-design-tokens
• [ ] @esri/eslint-plugin-calcite-components

Esri team

Calcite (design)

[macandcheese]

Seems like --calcite-panel-footer-space already exists, missed that. Request stands for header-content 😄