Merge experimental/c-cpp with core

[DavidKorczynski]

Merge the logic that is used to generate oss-fuzz integrations from scratch (https://github.com/google/oss-fuzz-gen/tree/main/experimental/c-cpp) with the core oss-fuzz-gen logic. The primary goal is to enable using the core prompt generation logic in combination with auto-building procedures and to make sure improvements in one benefits both.

[DavidKorczynski]

Refs for merging the code bases: https://github.com/google/oss-fuzz-gen/pull/440#discussion_r1667672538 and https://github.com/google/oss-fuzz-gen/pull/440#discussion_r1667666905