Tests: Add test for post titles containing percentage followed by numbers

[himanshupathak95]

Trac Ticket: #3329

This PR adds a unit test to verify that post titles containing percentage signs followed by numbers (e.g., %10) generate the correct permalinks. The test ensures that:

1. The post slug is generated correctly preserving the %10
2. The permalink contains the correct slug
3. The post can be queried using the generated slug

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