Apply a `urldecode` before processing the text

Summary/Problem motivation

When accessing the field's "processed" value through JSON:API it "double" encodes special characters like "%" in which are being produced usually by HTML encoding. E.g. /sites/default/files/inline-images/Iceland%20Context%20box.jpg becomes https://[siteurl]/sites/default/files/inline-images/Iceland%2520Context%2520box.jpg.

Steps to reproduce

1. Enable "Convert relative paths to absolute URLs" filter on the Text Format
2. Use the text editor and upload an image with a (space) " ".
3. Access the field/content through JSON:API

Proposed resolution

Do a `urldecode` first before processing the text.