Feature: Profile tool: Add support for subsections indicator

Description

This PR allows to display subsections indicator as vertical lines in the profile tool. This is based on the ideas discussed in https://github.com/qgis/QGIS-Enhancement-Proposals/issues/260
It works on the Elevation Profile and the Print Layout. In both cases, it is possible to change the symbology of the lines. For the elevation profile, theses new options are added to the options menu.

Screenshots

Elevation Profile

Layout

cc @Simon-Lopez @T4mmi @Djedouas

This feature was funded by BRGM

This feature was developed by Jean Felder