move `installation-testing` to experimental

[rogerthatdev]

Problem

installation-testing is a directory in the repo root with its own terraform, build files, and Dockerfile. It could be moved to experimental until ready to be integrated with Emblem's primary terraform and build files.

Expected behavior

As an optional extension of Emblem, 'installation testing' can still be included with the rest of Emblem terraform directory as a testing module that is optionally deployed at setup or after.

[rogerthatdev]

closing as obsolete