Speculation rules: URL patterns need escaping to work correctly when special characters are present

[jeremyroman]

Bug Description

If WordPress is deployed with an unusual path prefix (notably WordPress Playground uses something like /scope:0.123456/), this isn't properly escaped and the resulting patterns fail to parse.

Steps to reproduce

1. Go to https://playground.wordpress.net/?plugin=speculation-rules.
2. Open one of the pages at the top level.
3. Observe that there are errors in the developer console resulting pages.

Screenshots

n/a

Additional Context

• PHP Version: 7.4
• OS: Linux
• Browser: Chrome (121 beta)
• Plugin Version: trunk
• Device: Linux desktop

[jeremyroman]

This probably needs the following labels, though I don't think I have permission to apply them:

• [Focus] JS & CSS
• [Module] Speculation Rules
• Performance Lab Plugin

[westonruter]

Done in #951