Update Rust crate flume to 0.12.0

[renovate]

This PR contains the following updates:

Package	Type	Update	New value	References	Sourcegraph
flume	dependencies	minor	0.12.0	source

Test plan: CI should pass with updated dependencies. No review required: this is an automated dependency update PR.

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Release Notes

zesterer/flume (flume)

v0.12.0

Added

• fastrand feature

Removed

• nanorand feature

Fixed

• Panic when using Duration::MAX as timeout

v0.11.1

Added

• SendSink::sender
• SendFut, SendSink, RecvFut, RecvStream, WeakSender, Iter, TryIter, and IntoIter now implement Debug
• Docs now show required features

Removed

Changed

• WeakSender is now Clone
• spin feature no longer uses std::thread::sleep for locking except on Unix-like operating systems and Windows
• Flume is now in casual maintenance mode.

Fixed

v0.11.0

Added

• WeakSender, a sender that doesn't keep the channel open
• Sender/Receiver::sender_count/receiver_count, a way to query the number of senders and receivers attached to a channel
• Sender/Receiver::same_channel, a way to determine whether senders and receivers are attached to the same channel

Changed

• Relaxed some API features
• Make all remaining spinlocks opt-in

Fixed

• Fixed a rare race condition in the async implementation

v0.10.14

Fixed

• Fixed unbounded memory usage in RecvFut::poll_inner

v0.10.13

Added

• SendSink::sender, to get the sender of a SendSink

v0.10.12

Changed

• Updated nanorand to 0.7

v0.10.11

Fixed

• Out-of-order bug when using channels asynchronously

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