fix: Output parity between per-file and monolithic rule

[furtib]

Why:
We want the per-file rule to be a drop-in replacement for the monolithic rule.
For this, we want as little difference between the two rules as possible.
Currently, the monolithic rule's output layout is:

rule-name/
├── codechecker-files/
│   ├── data
│   ├── result.txt
│   ├── result.json
│   └── report
├── config
└── etc...

While the per-file rule's is:

rule-name/
├── data
├── config
└── etc...

What:

• Moved the data folder of the per-file rule under a codechecker-files folder

Addresses:
none