♻️ Refactor devenv build mechanism

This introduces multistage build process for devenv making
different dependencies build depend on its own (per example, when
jvm version is changed, only the jvm stage is rebuild)

This commit also introduces imagemagick 7.x custom build
in the same way as we have on public docker images, so on
devenv we use the same version.

backend/scripts/start-dev

@@ -36,9 +36,6 @@ export PENPOT_MEDIA_MAX_FILE_SIZE=104857600
 # Setup default multipart upload size to 300MiB
 export PENPOT_HTTP_SERVER_MAX_MULTIPART_BODY_SIZE=314572800
 
-# Enable ImageMagick v7.x support
-# export OPTIONS="-J-Dim4java.useV7=true $OPTIONS";
-
 # Initialize MINIO config
 mc alias set penpot-s3/ http://minio:9000 minioadmin minioadmin -q
 mc admin user add penpot-s3 penpot-devenv penpot-devenv -q
@@ -61,6 +58,7 @@ export JAVA_OPTS="\
        -Djdk.attach.allowAttachSelf \
        -Dlog4j2.configurationFile=log4j2-devenv.xml \
        -Djdk.tracePinnedThreads=full \
+       -Dim4java.useV7=true \
        -XX:-OmitStackTraceInFastThrow  \
        --sun-misc-unsafe-memory-access=allow \
        --enable-preview \