Fix use after free issue of EventDispatcher LatencyRecorder

[chenBright]

What problem does this PR solve?

Issue Number: resolve #3265

Problem Summary:

1. Use-After-Free crash on process exit: In StopAndJoinGlobalDispatchers() (registered via atexit), the global bvar::LatencyRecorder pointers g_edisp_read_lantency and g_edisp_write_lantency are explicitly deleted. However, bvar's background sampler thread (bvar_sampler_collector) is a leaky singleton that is never joined or stopped. If the sampler thread is concurrently accessing these recorders when they are deleted, a Use-After-Free occurs.

2. Unnecessary "latency" prefix stripping in LatencyRecorder::expose().
   

   brpc/src/bvar/latency_recorder.cpp

   Lines 198 to 205 in be01d10

   	// User may add "_latency" as the suffix, remove it.
   	if (prefix.ends_with("latency") || prefix.ends_with("Latency")) {
   	prefix.remove_suffix(7);
   	if (prefix.empty()) {
   	LOG(ERROR) << "Invalid prefix2=" << prefix2;
   	return -1;
   	}
   	}

What is changed and the side effects?

Changed:

Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

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