BUG : Powershell installer will not work for versions below 5.0

The new powershell installer fails on older versions of Powershell (pre 5.0) due to lack of native support for GUID generation and file unzip.

**To Reproduce**
Steps to reproduce the behavior:
1 : Download the Powershell resident installer from your Remotely server.
2 : Attempt to install on any machine with a Powershell version prior to 5.0 (eg. Windows server 2012/2012r2)
3 : Installation fails.

**Remotely Version**
Server (can be found on about page): 2024.02.22.1231
Agent (can be found in device card): 2024.02.22.1231

**Expected Behavior**
Installation should complete normally.

**Desktop (please complete the following information):**
- OS: Windows Server 2012/2012r2 & earlier. Probably also early Win10 releases although I can't test them. Basically any Windows OS running a Powersehll version pre 5.0
- Version : Any Powershell < 5.0

**Additional Context**
This is a relatively simple issue to correct, there are only two unsupported functions used both of which have suitable replacements. I have attached a patch file with the necessary corrections to make the Powershell script compatible with all versions of Powershell (tested on 2.0 & 4.0 - can't test 1.0 as I don't have a test system to hand).

[remotely-powershell-patch.patch](https://github.com/immense/Remotely/files/14417965/remotely-powershell-patch.patch)

- [ X] I am running Remotely in Docker and not on my QNAP, Synology, or Internet Connected Toaster

Start with the PowerShell installer and the attached remotely-powershell-patch.patch, focusing on the two functions reported as unsupported before PowerShell 5.0. Reproduce the installation on PowerShell 2.0 or 4.0 and verify that the installer completes successfully on the listed older Windows versions.

Written by the indexing model from the issue text.