Continue image space initialization if the primary boot image is valid.

`BootImageLoader::LoadFromSystem` checks the return value of
`BootImageLayout::LoadFromSystem` and continues only if the return value
is true. Therefore, `BootImageLayout::LoadFromSystem` shouldn't return
false to abort image space initialization even if it fails to load a
boot image extension. However, before this change, when
`allow_in_memory_compilation` is false, `BootImageLayout::LoadFromSystem`
returns false when a boot image extension is unusable. This isn't
expected. It wasn't a problem before because
`allow_in_memory_compilation` was always true, but
`allow_in_memory_compilation` can be false starting from aosp/2219944,
so we need to fix this issue.

Bug: 247055146
Test: ArtGtestsTargetChroot
Change-Id: I866e8acd38df270896b4acb362876cd9addf02a1
3 files changed