[2.8.x] Escape Content-Disposition params according to WHATWG HTML living standard (backport #11571) by @mkurz

[mergify]

This is an automatic backport of pull request #11571 done by Mergify.
Cherry-pick of 8e787dd has failed:

On branch mergify/bp/2.8.x/pr-11571
Your branch is up to date with 'origin/2.8.x'.

You are currently cherry-picking commit 8e787dd65c.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   core/play-integration-test/src/it/scala/play/it/libs/JavaWSSpec.scala
	modified:   core/play-integration-test/src/it/scala/play/it/libs/ScalaWSSpec.scala
	new file:   core/play-java/src/test/resources/testassets/foo.txt
	modified:   core/play/src/main/java/play/mvc/Http.java
	modified:   core/play/src/main/scala/play/core/formatters/Multipart.scala
	new file:   transport/client/play-ahc-ws/src/test/resources/testassets/foo.txt
	modified:   transport/client/play-ahc-ws/src/test/scala/play/api/libs/ws/ahc/AhcWSSpec.scala

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   core/play-java/src/test/java/play/mvc/RequestBuilderTest.java
	both modified:   core/play/src/main/scala/play/api/http/Writeable.scala
	both modified:   core/play/src/test/scala/play/api/http/WriteableSpec.scala

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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