Add cloud function name validation and update deployment scripts

[amd-yan]

I used this script to set up our Data Cloud integration.

I made the following enhancements to this deployment scripts:

1. [Enhancement] I added a new variable CLOUD_FUNCTION_NAME for the cloud function names. By doing so, we can point the same blob storage to multiple Salesforce instances when needed.
2. [Bug Fix] the trimmed function name trims the string after appending "xxxx--event-function", this is may cause a problem when those are trimmed, and 3 functions will be the same name.
3. [Documentation] I also added an example of the Salesforce Sandbox into the comment for the login URL.

Let me know should you have any questions.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @amd-yan to sign the Salesforce Inc. Contributor License Agreement.