[GR-60235] Register reflectively-accessed types as unsafe allocated

[graalvmbot]

All reflectively-accessible classes are now registered for unsafe allocation. This removes "unsafeAllocated" from reachability-metadata.json, and was evaluated to have only a minimal impact on the resulting image size (see #9679). In effect, the following JSON registration:

{
  "reflection": [
    {
      "type": "registered.class.Name",
    }
  ]
}

will become equivalent to:

{
  "reflection": [
    {
      "type": "registered.class.Name",
      "unsafeAllocated": true
    }
  ]
}

In the same fashion, calling RuntimeReflection.register(clazz) from a feature will make clazz unsafe-allocatable at run-time.

Existing JSON metadata files using the flag will continue to be accepted by Native Image, with a warning printed once per build.

[zakkak]

This removes "unsafeAllocated" from reachability-metadata.json, and was evaluated to have only a minimal impact on the resulting image size (see #9679).

@loicottet as mentioned in #9679 (comment)

The maximum size impact (3%) on treating all types as unsafe allocated seems quite high.

As a result, we would still like to have the option to opt-out of this (i.e. to set unsafeAllocated to false). Could you please keep this functionality? I believe (in general) that it would be better to just switch the default instead of removing the options.

[zakkak]

FWIW, after evaluating this PR it seems that it adds more overhead than the registration of all fields (in the integration tests of Quarkus core). See quarkusio/quarkus#44864 (comment) for more details.