Add import endpoint for GraalVM build stats

[jerboaa]

Support importing metrics as produced by oracle/graal#4685

Example usage:

curl -w '\n' -H "token: 10fe0d58bdcccddcadda64ee2fc195a5b3c18cc8ba4661b77ca1c9383109d82d15fc4e86d73a637ff199379bb2251796db997d718cfe81e97bb5e10b9098562f" -H "Content-Type: application/json" --post302 --data @$(pwd)/build-stats.json http://127.0.0.1:8080/api/v1/image-stats/import
{"id":1,"created_at":"2022-06-30T17:29:38.141+00:00","tag":null,"img_name":"hello","generator_version":"GraalVM 22.3.0-dev Java 11 Mandrel Distribution","image_size_stats":{"id":1,"total_bytes":12464150,"code_cache_bytes":4181632,"heap_bytes":7233536,"other_bytes":1048982,"debuginfo_bytes":0},"jni_classes_stats":{"id":1,"classes":58,"fields":58,"methods":52},"reflection_stats":{"id":3,"classes":27,"fields":0,"methods":267},"build_perf_stats":{"id":1,"total_build_time_sec":-1.0,"num_cpu_cores":8,"total_machine_memory":33258110976,"peak_rss_bytes":2911281152,"cpu_load":6.414419832280913},"total_classes_stats":{"id":4,"classes":3725,"fields":6388,"methods":27122},"reachability_stats":{"id":2,"classes":2709,"fields":3430,"methods":12255}}

[Karm]

THX 🙏