chore: Bump ver: 0.5.0

[drmingdrmer]

Changelog

chore: Bump ver: 0.5.0

refactor: remove multi-namespace support from mvcc

Summary

The mvcc module's read/write/range API collapses from a
namespace-scoped, per-call sequence-bounded trait zoo into a
single-space view API: every Table, Snapshot, and View now
owns exactly one key-value space, and View itself implements the
resulting ViewApi trait directly.

Details

Removed the entire scoped_*/seq_bounded_* trait family
(ScopedApi, ScopedGet, ScopedRange, ScopedRead, ScopedSet,
ScopedSeqBoundedGet, ScopedSeqBoundedIntoRange,
ScopedSeqBoundedRange, ScopedSeqBoundedRangeIter, SeqBoundedGet,
SeqBoundedIntoRange, SeqBoundedRange, SeqBoundedRangeIter)
along with ViewNamespace, ViewKey, ViewValue, and the Commit
trait. Table's own lookups already covered the point/multi-key/range
cases, and key/value bounds now come from the crate's existing
MapKey/MapValue traits, so this whole parallel hierarchy was
redundant. The survivors are renamed into the view_* family, and a
new ReadAtSeq trait (read_at_seq.rs) provides the one remaining
per-call sequence-bounded read (get_at_seq/range_at_seq).

With ViewNamespace gone, Table, Snapshot, and View drop their
namespace type parameter (<S, K, V> becomes <K> / <K, D>).
Tables<K> is now a plain Table<K, V> instead of
BTreeMap<S, Table<K, V>>, so every method loses its space
argument.

• The per-namespace increments_seq() flag is replaced by a
  per-View with_tombstone_seq_increment() setting plus explicit
  set_without_seq_increment / fetch_and_set_without_seq_increment
  calls for callers that need the old opt-out behavior.
• Snapshot::commit() is gone. View::into_parts() now returns
  (reader, last_seq, changes) so callers merge with
  Table::merge() instead of going through a namespace-aware commit
  trait.
• View<K, D> now implements ViewRead, ViewWrite, and
  ViewRange directly, delegating to its own methods, so it
  satisfies the combined ViewApi bound — a compile-time assertion
  test guards that.
• Dropped namespace_view_no_seq_increase_test.rs, which only
  exercised the now-removed per-namespace increments_seq()
  behavior.

---

• Improvement

[xp-trumpet]

@xp-trumpet partially reviewed 31 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on drmingdrmer).