feat(chip): set default shape to soft for ios and md theme and round for ionic theme

Issue number: internal

What is the current behavior?

The shape property defaults to undefined which evaluates to the "Soft" shape for the ionic theme and the "Round" shape for the ios/md themes.

Property Value	CSS Value (`ionic`)	CSS Value (`ios`)	CSS Value (`md`)
`undefined`	`4px`	`16px`	`16px`
`"round"`	`999px`	unsupported	unsupported
`"rectangular"`	`0px`	unsupported	unsupported

What is the new behavior?

Property Value	CSS Value (`ionic`)	CSS Value (`ios`)	CSS Value (`md`)
`"soft"`	`4px`	`10px`	`8px`
`"round"`	`999px`	`999px`	`999px`
`"rectangular"`	`0px`	`0px`	`0px`

Sets the default shape property to "soft" for ios and md themes and "round" for the ionic theme.
Updates the border-radius to apply to the shape classes instead of :host
Updates the ios theme to use 10px for "soft" as this was taken from the App Store:
Updates the md theme to use 8px for "soft" as this is taken from the Material Design 3 guidelines & the previous value of 16px is the equivalent of the 999px round shape due to the height being 32px
Adds support for the "round" and "rectangular" shapes in ios and md themes

Does this introduce a breaking change?

[x] Yes
[ ] No

BREAKING CHANGE:

The border-radius of the ios and md chip now defaults to 10px and 8px, respectively, instead of 16px in accordance with the iOS and Material Design 3 guidelines. To revert to the previous appearance, set the shape to "round", or override the --border-radius CSS variable to specify a different value.

ionic-team / ionic-framework