Allows consumer to toggle the visibility of the chart's legend values

feat(GlStackedColumnChart): Add `includeLegendAvgMax` prop

Closes #2267

See merge request !4499



Merged-by: Lukas Eipert <leipert@gitlab.com>
Approved-by: Artur Fedorov <afedorov@gitlab.com>
Approved-by: Amelia Bauerly <abauerly@gitlab.com>
Approved-by: Libor Vanc <5022246-lvanc@users.noreply.gitlab.com>
Approved-by: Lukas Eipert <leipert@gitlab.com>
Reviewed-by: Artur Fedorov <afedorov@gitlab.com>
Reviewed-by: Rudy Crespo <rcrespo@gitlab.com>
Co-authored-by: Rudy Crespo <rcrespo@gitlab.com>

# [90.1.0](gitlab-org/gitlab-ui@v90.0.0...v90.1.0) (2024-08-22)

### Features

* **GlStackedColumnChart:** Add `includeLegendAvgMax` prop ([70874ae8](gitlab-org/gitlab-ui@70874ae8))