fix: remove sun.misc for OSGi imports on Java 11 or newer

[rombert]

No longer require sun.misc in OSGi environments running Java 11 or newer.

The sun.misc requirement is only mandatory for Java 8 but this was not reflected in the OSGi requirements,
leading to additional friction when deploying the bundle.

This change post-processes all multi-version manifests to no longer require sun.misc.

Fixes #3338

[rombert]

I've tested this on a vanilla distribution of Apache Felix and installed the prerequisites

    9|Active     |    1|JSpecify annotations (1.0.0)|1.0.0
   10|Active     |    1|reactive-streams-jvm (1.0.4)|1.0.4

I've installed a SNAPSHOT build of the bundle, and when running Felix with Java 8 the bundle does not resolve

ERROR: Bundle io.projectreactor.reactor-core [12] Error starting file:/home/robert/sources/oss/reactor-core/reactor-core/build/libs/reactor-core-3.8.5-SNAPSHOT.jar (org.osgi.framework.BundleException: Unable to resolve io.projectreactor.reactor-core [12](R 12.0): missing requirement [io.projectreactor.reactor-core [12](R 12.0)] osgi.wiring.package; (osgi.wiring.package=sun.misc) Unresolved requirements: [[io.projectreactor.reactor-core [12](R 12.0)] osgi.wiring.package; (osgi.wiring.package=sun.misc)])
org.osgi.framework.BundleException: Unable to resolve io.projectreactor.reactor-core [12](R 12.0): missing requirement [io.projectreactor.reactor-core [12](R 12.0)] osgi.wiring.package; (osgi.wiring.package=sun.misc) Unresolved requirements: [[io.projectreactor.reactor-core [12](R 12.0)] osgi.wiring.package; (osgi.wiring.package=sun.misc)]
	at org.apache.felix.framework.Felix.resolveBundleRevision(Felix.java:4398)
	at org.apache.felix.framework.Felix.startBundle(Felix.java:2308)
	at org.apache.felix.framework.Felix.setActiveStartLevel(Felix.java:1566)
	at org.apache.felix.framework.FrameworkStartLevelImpl.run(FrameworkStartLevelImpl.java:297)
	at java.lang.Thread.run(Thread.java:750)

Running headers 12 | grep misc shows that the Import-Package for sun.misc is there .

When running on Java 21 the bundle is active and requirement for the sun.misc import is missing.

Also, I tried making the change more gradle-idiomatic but I did not really find a way to do so; it seems that the bnd multi-release jar functionality does not allow tweaking the manifest. Happy to take feedback if anyone sees a different way of removing the jars.