Bundle small script files into a single file

As Azure PowerShell grows there are more and more script files in autorest-based modules. Most of them are for customization.
(As of today, there are 663 custom scripts, 289 of them are in-memory object creation scripts.)

Although it is convenient for developing & debugging, having so many small files have these **disadvantages**:
- Each script needs to be signed per company's policy. It's time consuming (>10min).
- It's effiency than one single large file in the perspective of IO

One **solution** is to bundle the small scripts into one single source file, but we need to figure out these problems:
- Can we mo sacrifice developing & debugging experience?
- What time to bundle script files?

[Attachment: a complete list of scripts in Azure PowerShell](https://github.com/Azure/autorest.powershell/files/9250358/sign-scripts.txt)