URI Encoding inconsistent between SSR and Browser routers

[Bluebie]

Describe the bug

A reasonable user would expect the SvelteKit router to behave the same way in the ssr and browser contexts, regarding uri encoding in route params. This currently isn't the case.

Sample below demonstrates main issue, but also note this inconsistency appears in load functions too, depending if they are run in ssr or browser side

Reproduction

git clone https://github.com/Bluebie/sveltekit-url-params-encoding-issue.git
cd sveltekit-url-params-encoding-issue
npm i
npm run dev

Open browser to http://localhost:3000/test/foo and click the demo links in the list on the bottom of the page to see some examples of how decoding is inconsistent.

Logs

No response

System Info

System:
    OS: macOS 12.3.1
    CPU: (8) arm64 Apple M1
    Memory: 80.17 MB / 8.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 17.8.0 - /opt/homebrew/bin/node
    npm: 8.5.5 - /opt/homebrew/bin/npm
  Browsers:
    Chrome: 100.0.4896.88
    Edge: 100.0.1185.39
    Firefox: 97.0.1
    Safari: 15.4
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.34 
    @sveltejs/kit: next => 1.0.0-next.312 
    svelte: ^3.46.0 => 3.47.0

Severity

serious, but I can work around it

Additional Information

Example output of src/routes/test/[param].svelte when navigating to http://localhost:3000/test/why%3Ais%3Acolon

[Yazan-0]

the current behavior is of decodeURI instead of decodeURIComponent

[rdela]

see #5029 / #5056

[benmccann]

I upgraded the test project and it's still failing: Bluebie/sveltekit-url-params-encoding-issue#1