Bump sled from 0.26.3 to 0.27.0

[dependabot-preview]

Bumps sled from 0.26.3 to 0.27.0.

Release notes

Sourced from sled's releases.

async flush, bugfixes, event variant rename

Breaking Changes

• Event::Set has been renamed to Event::Insert and
  Event::Del has been renamed to Event::Remove. These
  names better align with the methods of BTreeMap from
  the standard library.

Bug Fixes

• A deadlock was possible in very high write volume
  situations when the segment accountant lock was
  taken by all IO threads while a task was blocked
  trying to submit a file truncation request to the
  threadpool while holding the segment accountant lock.

New Features

• flush_async has been added to perform time-intensive
  flushing in an asynchronous manner, returning a Future.

Changelog

Sourced from sled's changelog.

0.27

Breaking Changes

• Event::Set has been renamed to Event::Insert and
  Event::Del has been renamed to Event::Remove. These
  names better align with the methods of BTreeMap from
  the standard library.

Bug Fixes

• A deadlock was possible in very high write volume
  situations when the segment accountant lock was
  taken by all IO threads while a task was blocked
  trying to submit a file truncation request to the
  threadpool while holding the segment accountant lock.

New Features

• flush_async has been added to perform time-intensive
  flushing in an asynchronous manner, returning a Future.

0.26.1

Improvements

• std::thread is no longer used on platforms other than
  linux, macos, and windows, which increases portability.

0.26

New Features

• Transactions! You may now call Tree::transaction and
  perform reads, writes, and deletes within a provided
  closure with a TransactionalTree argument. This
  closure may be called multiple times if the transaction
  encounters a concurrent update in the process of its
  execution. Transactions may also be used on tuples of
  Tree objects, where the closure will then be
  parameterized on TransactionalTree instances providing
  access to each of the provided Tree instances. This
  allows you to atomically read and modify multiple
  Tree instances in a single atomic operation.
  These transactions are serializable, fully ACID,
  and optimistic.
• Tree::apply_batch allows you to apply a Batch
• TransactionalTree::apply_batch allow you to
  apply a Batch from within a transaction.

... (truncated)

Commits

• See full diff in compare view

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[codecov]

Codecov Report

Merging #359 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #359   +/-   ##
=======================================
  Coverage   65.16%   65.16%           
=======================================
  Files         106      106           
  Lines       12037    12037           
=======================================
  Hits         7844     7844           
  Misses       4193     4193

[codecov]

Codecov Report

Merging #359 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #359   +/-   ##
=======================================
  Coverage   65.16%   65.16%           
=======================================
  Files         106      106           
  Lines       12037    12037           
=======================================
  Hits         7844     7844           
  Misses       4193     4193

[tomtau]

seems ok, but preparation of integration test fails -- @calvinaco may investigate