Upgrade Emscripten version

[brandonpayton]

Motivation for the change, related issues

Note: This work is continued from a PR started under the WordPress GH org.

There are a couple of reasons for this upgrade:

1. I am having trouble rebuilding php-wasm on my current system. References to older ubuntu images and emscripten versions has given me trouble.
2. We want this Emscripten fix from @jeroenpf and @bgrgicak which was first included in Emscripten 3.1.73. This should address https://github.com/Automattic/dotcom-forge/issues/8815.

Implementation details

This PR:

• Bumps the ubuntu docker image version due to build errors related to missing image. Referencing a newer ubuntu image seemed to fix the "missing image" errors.
• Bumps Emscripten version
• Adjusts Playground-specific patches to Emscripten output since the latest breaks that patching.

Testing Instructions (or ideally a Blueprint)

• CI

[brandonpayton]

This PR needs a bit more work to fix patches Emscripten build output. I hope to work on that tomorrow.

[brandonpayton]

Closing. This is the wrong place for this work.