Add unit tests for `StreamPeerTCP` #69518

Job	Run time
📊 Static checks / Code style, file formatting, and docs	2m 0s
🤖 Android / Template arm32 (target=template_release, arch=arm32)	6m 31s
🤖 Android / Template arm64 (target=template_release, arch=arm64)	6m 31s
🍏 iOS / Template (target=template_release)	1s
🤖 Android / Editor (target=editor)	6m 31s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=mold)	6m 31s
🐧 Linux / Editor w/ Mono (target=editor)	6m 30s
🐧 Linux / Template w/ Mono, debug (target=template_debug)	6m 25s
🐧 Linux / Template w/ Mono, release (target=template_release)	6m 31s
🐧 Linux / Editor with clang sanitizers (target=editor, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	6m 31s
🐧 Linux / Minimal template (target=template_release, everything disabled)	6m 31s
🐧 Linux / Editor with ThreadSanitizer (target=editor, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	6m 31s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	6m 31s
🌐 Web / Template w/o threads (target=template_release, threads=no)	6m 31s
🍎 macOS / Template (target=template_release)	1s
🍎 macOS / Editor (target=editor)	1s
🏁 Windows / Template (target=template_release)	6m 30s
🏁 Windows / Editor (target=editor)	6m 32s
🏁 Windows / Editor w/ clang-cl (target=editor, use_llvm=yes)	6m 30s
🏁 Windows / Template w/ GCC (target=template_release, use_mingw=yes)	6m 29s
	1h 46m 9s

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