Bump BREEs to Java 1.8 for java.util.Optional

FrameworkUtil now uses it internally so compiling bundles with older
BREEs lead to errors like:
[ERROR] /home/jenkins/agent/workspace/ecf-tycho.gerrit/TARGET_PLATFORM/2021-09/providers/bundles/org.eclipse.ecf.provider.filetransfer.httpclient45/src/org/eclipse/ecf/internal/provider/filetransfer/httpclient45/HttpClientProxyCredentialProvider.java:[195]
[ERROR] 	String os =
FrameworkUtil.getBundle(HttpClientProxyCredentialProvider.class).getBundleContext().getProperty(OSGI_OS);
[ERROR]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[ERROR] The type java.util.Optional cannot be resolved. It is indirectly
referenced from required .class files
[ERROR] 1 problem (1 error)

Change-Id: I5e4f237afb943cbe7234c5bac5633bbb900fb43c