runtime: use hchan-style channel queues

[zhouguangyuan0718]

Summary

• Rework llgo channels around hchan-style state: buffered ring metadata plus explicit send and receive wait queues.
• Replace the old single pending recv/select state with per-waiter queue nodes, so multiple goroutines and select cases can wait on the same channel safely.
• Implement select waiters with a shared select state and one-shot claim, so only one case can win while the losing waiters are removed from their channel queues.
• Lock all distinct channels in address order for blocking select registration to avoid multi-channel lock-order deadlocks.
• Preserve closed-channel semantics: receive drains buffered values then returns zero/ok=false, send panics, and close wakes recv/send waiters without leaving the channel locked.

Design Notes

• Chan now tracks qcount/dataqsiz/buf/recvx/sendx plus sendq and recvq.
• Blocking send/recv first try the fast path under the channel mutex. If not ready, they enqueue a chanWaiter and sleep on a condvar.
• Waiter/select completion is represented by one waitStatus state machine instead of separate done, recvOK, panicOnWake, and claimed booleans.
• waitClaimed keeps select two-phase completion safe: a case can reserve the select result before copying data, and only the final status wakes the select goroutine.
• Unbuffered rendezvous copies directly between sender and receiver waiters.
• Buffered receive pulls from the ring buffer and then admits one queued sender into the freed slot.
• Blocking select first tries a non-blocking pass. If no case is ready, it sorts/dedups channels, locks them, retries under locks, enqueues waiters, unlocks, and sleeps on the shared selectState.
• The inline channel list uses [selectInlineChanCount]*Chan and spills to a slice when a select references more distinct channels.

Tests

• /opt/data/tmp/llgo-pr-split/llgo-channel test -timeout=180s ./test -run 'Test(ClosedChannelSendPanicDoesNotKeepChannelLocked|SelectDuplicateChannelDoesNotDeadlock|ConcurrentSelectProposeReplyStress)' -count=1

Added Coverage

• closed-channel send panic does not leave the channel unusable
• duplicate-channel select does not deadlock
• concurrent select request/reply stress makes progress

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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