[23b] switch to spack v0.19.2

In the meeting today (09/08/23), we decided to switch to spackv0.19.2 for the following reasons:

• incorrect order of dependencies in the spack env loads command. https://github.com/spack/spack/issues/39095
• inconsistent behaviour of overloading dependency between spack v0.19 and spack v0.20

Changes to be reverted:

• add libxc+kxc package to spack v0.19 fork
• change module blacklist command