[llvm][Support] Improvements to ListeningSocket functionality and documentation (#84710)

Improvements include
* Enable `ListeningSocket::accept` to timeout after a specified amount
of time or block indefinitely
* Enable `ListeningSocket::createUnix` to handle instances where the
target socket address already exists and differentiate between
situations where the existing file does and does not already have a
bound socket
* Doxygen comments

Functionality added for the module build daemon

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Co-authored-by: Michael Spencer <bigcheesegs@gmail.com>