GlTable: Add tooltips to provide more information about table sorting

Background

Related to gitlab#330478 (closed), the current sorting indicator for table columns does not give enough information about how the sorting is applied to the column. We should extend the table headers to provide additional useful information to users on how the field is sorted.

JTBD:

We should:

• Add support for tooltips to describe how the table columns are sorted
• Provide default descriptions for common sorting, based on the type of the field
• Provide an optional field to customize the description of the field

Default descriptions

Alphabetical values

• Sort a→z for arrow down ⬇️
• Sort z→a for arrow up ⬆️

Numerical values

• Sort low→high for arrow down ⬇️
• Sort high→low for arrow up ⬆️

Time-based values

• Sort new→old for arrow down ⬇️
• Sort old→new for arrow up ⬆️

Example