feat(table): Show sort icon by default

### Feature Description

When a table column or multiple columns have a sorting option, it is not visually obvious until you accidentally or intentionally hover over the column header. This behavior is not intuitive, as shown in the screenshot and example:

https://material.angular.io/components/table/examples#table-sorting

**So, the proposal is to add an option to make the sort icons visible by default, as shown in the examples:**

_Example 1:_


_[Example 2](https://primeng.org/table#sort):_


Start by comparing the Material table sorting example and the linked PrimeNG table sorting example to understand the requested default icon behavior. Trace the table sorting implementation and determine how an option should expose always-visible sort icons; done means sortable columns can show their icons without hover while existing sorting behavior remains unchanged.

Written by the indexing model from the issue text.