MSI installer uses 32-bit powershell for running the permission.ps1 script

Hi!

I've noticed that some of actions that CWA MSI installer runs on Windows are using 32-bit registry lookup and subsequently powershell to run `permission.ps1` script. There is nothing wrong with that per se, it works on most setups, but in some rare cases, using 32-bit powershell is not desirable/possible in the 64-bit environment. Overriding POWERSHELLEXE parameters doesn't solve the issue completely as well, as 32-bit powershell is still being used under the hood:

Assuming everything about the CWA build and packaging is already 64-bit, is there any reason these operations remain 32-bit (at least from the consistency point of view)?

If I apply a few transformations to the default AWS MSI with just 2 changes equivalent to the following WSX operations, all subsequent operations are done by the 64-bit powershell:
* `s/WixQuietExec/WixQuietExec64/` in https://github.com/aws/amazon-cloudwatch-agent-test/blob/df584e59883d973a3664677fe8cd055ffe41b78d/msi/tools/amazon-cloudwatch-agent.wxs#L176-L181. [docs](https://wixtoolset.org/docs/v3/customactions/qtexec/#running-64-bit-executables)
* Add `Win64='yes'` to `RegistrySearch` in https://github.com/aws/amazon-cloudwatch-agent-test/blob/df584e59883d973a3664677fe8cd055ffe41b78d/msi/tools/amazon-cloudwatch-agent.wxs#L28-L32 [docs](https://wixtoolset.org/docs/v3/xsd/wix/registrysearch/)

I'm happy to submit a patch if you think the changes above are a good idea, otherwise sorry for the noise!

Thanks in advance!

Start with msi/tools/amazon-cloudwatch-agent.wxs, especially the RegistrySearch and custom-action sections linked in the issue, and read the referenced WiX documentation for 64-bit execution and registry searches. Verify the MSI’s permission.ps1 path and registry lookup on a 64-bit Windows environment; done means those operations consistently use 64-bit PowerShell without breaking installation.

Written by the indexing model from the issue text.