Add OracleDatabase/21.3.0-XE project

[PaulNeumann]

Adds an OracleDatabase/21.3.0-XE project, based on the OracleDatabase/18.4.0-XE project.

Notable changes from the 18.4.0-XE project:

• Use Oracle Linux 8 instead of Oracle Linux 7

• Increase default VM memory to 2300 MB (approximately 2.25 GB) to avoid memory warning during installation

• 21c Oracle homes are read-only by default, so the tnsnames.ora file is in ORACLE_BASE_HOME/network/admin, instead of ORACLE_HOME/network/admin

• install.sh script:

  • Address all ShellCheck warnings
  • Remove unnecessary use of sudo (script runs as root)
  • Ensure that permissions on setPassword.sh are set correctly
  • Minor formatting fixes (trailing spaces, single vs. double quotes, etc.)

Tested with both VirtualBox and libvirt/KVM. Closes #380.

I'm happy to make any changes that you'd like.

Signed-off-by: Paul Neumann 38871902+PaulNeumann@users.noreply.github.com

[gvenzl]

Thanks a lot for your contribution, @PaulNeumann!