4.x: Add optional build/test for future JDKs (#8077)

* 4.x: Add optional build/test for future JDKs

* try temurin builds

* use toolchain override

* Run Gradle on 26, invoke toolchain for 27

* Minor log fix

* hope gradle runs on 26

* Don't run jacoco on EA as it breaks its assembly parser

* another attempt at running Gradle on 26 and code on 27

* Fix jacoco again

* fix java home

* No jacoco for experimentals

4.x: Upgrade to Java 26 baseline compilation, test isolation (#8074)

Update README.md to show our fancy openssf badge

4.x: Add optional build/test for future JDKs (#8077)

* 4.x: Add optional build/test for future JDKs

* try temurin builds

* use toolchain override

* Run Gradle on 26, invoke toolchain for 27

* Minor log fix

* hope gradle runs on 26

* Don't run jacoco on EA as it breaks its assembly parser

* another attempt at running Gradle on 26 and code on 27

* Fix jacoco again

* fix java home

* No jacoco for experimentals

4.x: Report back test failures in a readable manner for PRs/Snaps (#8066

)

* 4.x: Report back test failures in a readable manner for PRs/Snaps

* gradle_pr.yml `test_failures` -> `test failures`

4.x: Intro Schedulers.virtual(), deprecate Schedulers.io(), fix tests (…

…#8051)

* 4.x: Intro Schedulers.virtual(), deprecate Schedulers.io(), fix tests

* Add TCK tests, fix other tests

org.reactivestreams -> java.util.concurrent.Flow in docs

Update release-notify-x.yml

Create release-notify-x.yml

Don't want to manually post on X every time there is a release...

Update push_javadoc.sh

make the 4.x/javadoc directory if doesn't exist