Docker images don't build on M1 mac

[bcipriano]

Subissue of #1204.

Describe the bug
OpenCue Docker images fail to build on M1 mac due to the arm64 architecture. Upstream images are pulled with arm64 architecture by default and this causes a variety of issues, mostly around dependencies not existing for that platform.

Cuebot image fails with:

Step 1/29 : FROM gradle:6.0.1-jdk11 AS build
6.0.1-jdk11: Pulling from library/gradle
no matching manifest for linux/arm64/v8 in the manifest list entries

CueGUI image fails to install the PySide2 dependency as it doesn't exist for arm platforms. See #1194.

To Reproduce
Run docker build commands on an M1 mac.

docker build -t opencue/cuebot -f cuebot/Dockerfile .

docker build -t opencue/cuegui -f cuegui/Dockerfile .

Expected behavior
Images should build without error and be as consistent as possible across platforms.

Version Number
e7c38c6