Introduce expression support in RasterSymbolizer GammaValue

Description

In particular to support env variables, but not limited to that.
Currently only some attributes / elements support values as expressions.
We would like to introduce support for GammaValue.
Depends on https://osgeo-org.atlassian.net/browse/GEOT-6112

Environment

None

Status

Assignee

Mauro Bartolomeoli

Reporter

Mauro Bartolomeoli

Triage

None

Fix versions

Affects versions

Components

Priority

Medium
Configure