During hot module replacement (HMR), updating component inline styles
(`<style>`) or external stylesheet URLs (`<link rel="stylesheet">`) previously
triggered a complete destruction and recreation of matching component view
trees (`LView`). This caused loss of live application state (such as input
values, scroll positions, component signal state, and iframe instances) whenever
a CSS or SCSS file was edited.

This change introduces `replaceStyles` on `SharedStylesHost`, allowing HMR to
mutate inline style `textContent` or link `href` attributes in-place. The method
accepts an `isScoped` flag (`oldDef.encapsulation !== ViewEncapsulation.None`)
to distinguish component-scoped styles from un-encapsulated styles:
- For scoped styles (`isScoped === true`), in-place mutation and tracking
  record re-keying runs regardless of `record.usage`, preserving active instance
  usage counts so that multi-instance components unmount cleanly without premature
  style removal.
- For unscoped styles (`isScoped === false`), if `record.usage > 1`, it falls
  back to `removeUsage` + `addUsage` to protect other component classes sharing
  identical un-encapsulated initial CSS.

If non-style metadata (such as `template`, `inputs`, `outputs`, `providers`,
`hostBindings`, `selectors`, or `hostDirectives`) or encapsulation (`ShadowDom`)
changes alongside styles, HMR safely falls back to view tree recreation.