Doc: The default sorting alg. is stable from 1.9 (#47579)
* Update doc/src/base/sort.md
* Update docs: The default sorting alg. is stable
* Compat 1.9 for QuickSort to be stable
* Specify the default algorithm
* Use example from InlineStrings.jl
* Change example to jldoctest
* Remove "*appear* to be stable." as slightly misleading.
Co-authored-by: Lilith Orion Hafner <lilithhafner@gmail.com>
