UseSWIG: Transform swig depfile to match Ninja generator paths

Since !5724 (merged) we use a tool-provided depfile to extract dependencies under the Ninja generator. Enable CMP0116 to ensure depfile paths are translated to match what the Ninja generator writes to the build manfiest.

Also backport !5802 (merged) to the 3.20 release branch. Projects need to be able to control policies.

Fixes: #22029 (closed)
Backport: release:HEAD^2
Topic-rename: UseSWIG-policies