feat(modal): add component tokens (#8951)

**Related Issue:** #7180

## Summary

Adds the following component tokens (CSS props):

* `--calcite-modal-accent-color`
* `--calcite-modal-background-color`
* `--calcite-modal-border-color`
* `--calcite-modal-close-button-background-color-hover`
* `--calcite-modal-close-button-background-color`
* `--calcite-modal-close-button-icon-color`
* `--calcite-modal-content-background-color`
* `--calcite-modal-content-space`
* `--calcite-modal-corner-radius`
* `--calcite-modal-scrim-background-color`
* `--calcite-modal-shadow`
* `--calcite-modal-text-color`

Deprecates the following:

* `--calcite-modal-content-background`
* `--calcite-modal-content-padding`
* `--calcite-modal-scrim-background`

This additionally updates naming on internal props.