Bump gradle plugin versions previously blocked by Java8 support

[Abacn]

Now we dropped Java8 support to build Beam, we can bump the following plugins

• Shadow plugin to 8.3.8

• grgit-gradle to 5.3.2

• Remove Java8 logic for Errorprone

As a result now it requires Java11+ to build Beam (Part of #31678).

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[Amar3tto]

This PR breaks #35605, #34989, #34126, #32949

[Abacn]

Fixing in #35609