ProvenanceStorage: Use separate path for 'provenance' and 'nested provenance'

[fviernau]

The local file storage uses separate paths for provenance and nested provenance, see [1].
For HTTP file storage only a single path can be used.

Task: Separate the paths also for HTTP file storage.

[1]

ort/scanner/src/main/kotlin/provenance/NestedProvenanceStorage.kt

Line 50 in a65a9a6

LocalFileStorage(ortDataDirectory.resolve("$TOOL_NAME/nested_provenance"))

[sschuberth]

@fviernau is still something we should tackle?

[fviernau]

@fviernau is still something we should tackle?

IMO it still makes sense for consistency.