[C API] add rocksdb_set_db_options for dynamic DB option updates

[mjc2-stripe]

Context

The C API lacks a SetDBOptions wrapper, so callers using the C bindings cannot dynamically reconfigure DB-level options at runtime without dropping down to the C++ API.

Changes

• Add rocksdb_set_db_options to the C API as a wrapper around DB::SetDBOptions
• Adds new tests in c_test.c covering both valid and invalid option updates

[meta-codesync]

@xingbowang has imported this pull request. If you are a Meta employee, you can view this in D101010593.

[github-actions]

✅ clang-tidy: No findings on changed lines

Completed in 49.5s.

[mjc2-stripe]

Hey @jaykorean! Could you please take a look at this when you get the chance? Thanks!