JSSE: protect from calling freeSSL() while I/O operations in progress

[cconlon]

This PR adds an atomic counter of active I/O operations (read/write) to WolfSSLSocket.java to protect against calling freeSSL() while I/O ops are still in progress.

This fixes an issue where AddressSanitizer detected heap-use-after-free errors when multiple threads performed concurrent I/O operations while another thread called close() on the same WolfSSLSocket. The race condition occurred when wolfSSL_get_app_data() was called on a freed WOLFSSL object during active read/write operations.

I did try to get a unit test put together for regression on this item, but was unsuccessful in a reliable consistent test yet. Separate reproducer confirmed this fixed the issue locally.

[Copilot]

Pull Request Overview

The PR introduces an atomic counter to track active I/O operations in WolfSSLSocket and prevent freeSSL() from being called while reads or writes are in flight.

• Added activeOperations counter with enterIOOperation()/exitIOOperation() helpers.
• Wrapped read/write streams to increment/decrement the counter.
• Updated close() to defer freeing SSL until no active operations remain.

Comments suppressed due to low confidence (1)

src/java/com/wolfssl/provider/jsse/WolfSSLSocket.java:2735

• No tests were added to verify that activeOperations prevents freeSSL() under concurrent I/O, or that the counter remains accurate under failure paths. Consider adding multithreaded unit tests or integration tests that simulate concurrent read/write and close calls.

            /* Enter I/O operation to prevent use-after-free */