Improve usability of demonstration deployment deploy script

### User Story

As a user deploying Sleeper with the demonstration deploy script, I want to be able to specify the configuration files I want it to use clearly and unambiguously, so that I'm not surprised at which files it reads.

### Description / Background

We've had some confusion about table configuration being read when only instance configuration was passed to a script:

- https://github.com/gchq/sleeper/issues/6593

We'd like to improve the way demonstration deployment deploy script takes command line parameters, and let you point it to the configuration you want to use easily.

We'd like to match the setup of command line parameters used by the non-demonstration instance deploy new script. Those command line parameters are being set up in the following issue:

- https://github.com/gchq/sleeper/issues/6593

### Acceptance Criteria

**When** I deploy a demonstration instance
**Then** it should default, as it does now, to copying a template instance configuration with system test properties included
**And** I should be able to specify command line parameters consistent with the deploy new instance script

### Technical Notes / Implementation Details

At time of writing the demonstration deployment scripts are under `scripts/test/deployAll`.

The main deploy new instance script is at `scripts/deploy/deployNew.sh`.

### Dependencies / Blockers

Depends on:
- https://github.com/gchq/sleeper/issues/6593

Conflicts with:
- https://github.com/gchq/sleeper/issues/2384