Add audio sink renaming to LinkKit

[silver-ben]

LinkKit accepts a channel name when creating an audio sink, but has no public API to change it. Recreating the sink to rename it changes the channel ID, so receiving apps have to select the stream again.

Add ABLLinkAudioSinkSetName, forwarding to the existing LinkAudioSink::setName. This preserves the channel ID and existing receiver subscriptions. The header documents the name limit and non-thread-safe, non-realtime-safe contract.

Verified with Xcode 26.3 against the Link commit pinned by LinkKit CI, be64e5d1fe0cd01dea016ae31c2cefaddc0ce558:

• Release SDK builds for iOS, iOS Simulator and Mac Catalyst passed.
• Existing LinkKit tests passed.
• A standalone iOS 26.3 simulator probe using the modified LinkKit API and two peers on isolated loopback discovery observed the new name with the original channel ID. The original receiver source continued receiving samples generated only after the rename was observed. A sibling stream retained its name, ID and audio delivery.
• As a negative control, replacing the rename call with sink deletion and recreation caused the probe to reject the changed channel ID.

No application engine or changes to the Link dependency were needed for the implementation. Verification used a temporary standalone probe; no new test target is included.

[fgo-ableton]

Thank you!

[silver-ben]

Thank you!

You're welcome! Thanks for merging.