[Spark] Inject special characters in file paths in testing mode

[cstavr]

Which Delta project/connector is this regarding?

• [X] Spark
• [ ] Standalone
• [ ] Flink
• [ ] Kernel
• [ ] Other (fill in here)

Description

Change Rarquet and DV file names to use in testing mode a name prefix that contains special chars. This provides good coverage of handling special characters in paths for all Delta code.

How was this patch tested?

Test-only PR. Updated existing tests that were incorrectly handling paths.

Does this PR introduce any user-facing changes?

No