Enhance the automatic naming of string variables upon loading PDB

Version and Platform (required):

• Binary Ninja Version: 3.6.4802-dev, 87e27dc3
• OS: Windows
• OS Version: 11
• CPU Architecture: x86_64

Bug Description:
When loading a binary with a PDB file, BN employs unconventional variable names for string variables. These names could be enhanced for improved readability, as the current naming often blurs the distinction between variable names and variable types, leading to confusion. Additionally, this behavior makes it more challenging to copy code from the decompiler to plain C code.

Steps To Reproduce:

1. Load a binary that have a PDB file
2. Examine various string variables within the BNDB

Expected Behavior:
I expect BN to give those variables more simpler names. For the example above it could be sTotalAnimals. Essentially, BN could remove any characters from the variable names except for digits and alphabet letters, resulting in clearer naming.

Reproduce the naming behavior by loading a binary with a PDB file and examining string variables in the BNDB and decompiler output. Trace the code responsible for imported PDB variable names; done means string variable names are simpler and preserve only letters and digits, such as sTotalAnimals, without harming other names.