Add more release highlights

Merge pull request gradle#16218 from gradle/wolfs/normalization/fix-m…

…issing-inputs

Fix issue with file hash cache during runtime classpath normalization (6.8 backport)

Recognize contributor

Update release notes for milestone 1 release

Do not fail if test failure has no exceptions

refs gradle#15890

Update gradle-wrapper.properties to Gradle 6.8 RC5

Remove notes about incremental development improvements

Merge pull request gradle#15633 from gradle/cc/dm/fix-exclude-availab…

…le-at

Fix excludes being ignored when using `available-at`

Merge pull request gradle#15610 from gradle/wolfs/transforms/no-file-…

…deps-between-builds

Use mutable workspace provider for file dependencies

Merge pull request gradle#15610 from gradle/wolfs/transforms/no-file-…

…deps-between-builds

Use mutable workspace provider for file dependencies