The upstream refactoring in 4c89d31 (streaming: rely on object
sources to create object stream, 2025-11-23) changed how
istream_source() discovers objects. Previously, it called
odb_read_object_info_extended() with flags=0 to locate the object, then
tried the source-specific opener (e.g. open_istream_loose). If that
failed (e.g. corrupt loose object), it fell back to open_istream_incore
which re-read the object — by which time the read-object hook had
already re-fetched a clean copy.

After the refactoring, istream_source() iterates over sources directly.
When a corrupt loose object is found, odb_source_loose_read_object_stream
fails and the loop continues to the next source. When no source has the
object, it falls through to open_istream_incore, which calls
odb_read_object_info_extended with OBJECT_INFO_DIE_IF_CORRUPT. This
encounters the same corrupt loose file still on disk and dies before the
read-object hook gets a chance to re-download a clean replacement.

Fix this by clearing OBJECT_INFO_DIE_IF_CORRUPT in open_istream_incore
when GVFS_MISSING_OK is set, matching the existing pattern in
odb_read_object.

This fixes the GitCorruptObjectTests functional test failures
(GitRequestsReplacementForAllNullObject,
GitRequestsReplacementForObjectCorruptedWithBadData,
GitRequestsReplacementForTruncatedObject) that appeared when upgrading
from v2.50.1.vfs.0.1 to v2.53.0.vfs.0.0.

Signed-off-by: Tyler Vella <tyvella@microsoft.com>