Fix SQLite URLs with Python 3.12.4

[soininen]

Unparsing URL tuples using Python's standard library urllib functions has changed between Python 3.12.2 and 3.12.4 in a way that breaks SQLite URLs that point to a file. The incompatibility raises from the number of forward slashes after URL scheme that differs from previous Python versions and breaks SqlAlchemy's URL parsing. We now ensure that there is always three slashes between the scheme and the path.

No associated issue.

Checklist before merging

• [x] Documentation (also in Toolbox repo) is up-to-date
• [x] Release notes have been updated
• [x] Unit tests have been added/updated accordingly
• [x] Code has been formatted by black
• [x] Unit tests pass

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 78.20%. Comparing base (bcfdd07) to head (7b3a5d0).

Files	Patch %	Lines
spinedb_api/filters/tools.py	93.33%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #421 +/- ## ========================================== + Coverage 78.13% 78.20% +0.07% ========================================== Files 72 72 Lines 9543 9550 +7 Branches 2038 2039 +1 ========================================== + Hits 7456 7469 +13 + Misses 1748 1742 -6 Partials 339 339 ```

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