Fix a hot loop in DirectExchangeClient

[surajkn]

Description

The fix changes queuedClients to LinkedHashSet, this helps with the filter condition in scheduleRequestIfNecessary. In addition two for loops are modified to become one loop on Iterator.

Additional context and related issues

We experienced some performance regression as a result of https://github.com/trinodb/trino/commit/1ef442738fc51d1d7cf167bf6ca413378d928026 and this is an attempt to fix the same.

Release notes

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# Section
* Fix some things. ({issue}`issuenumber`)