Clean up noisy logs

Summary:
Previously, we were having two logs that will display on every job:

```
E1023 11:34:59.640702 2378951 Logger.cc:164] Thread Context Fn dict does not contain prefix NCCL
W1023 11:34:59.640872 2378951 Logger.cc:144] devvm26668:2378951:2378951 [0][main] NCCL WARN Prefix NCCL re-registering thread context fn
```

This is due to our change to logger. This has caused difficulty for developers to look at the log in jobs. Remove these logs by:
1. Change re-registering thread context fn log to debug level.
2. Add context fn to prefix in logger initialization.

Reviewed By: minsii

Differential Revision: D85368422

fbshipit-source-id: dce116fea80612ea4555c568ba657ae31f91424a

Author: YulunW

comms/utils/logger/Logger.cc

@@ -29,6 +29,8 @@ void NcclLogger::init(const NcclLoggerInitConfig& config) {
   if (!firstInit_.test_and_set()) {
     folly::initLoggingOrDie();
     DataTableWrapper::init();
+    NcclLogFormatterFactory::registerThreadContextFn(
+        config.logPrefix, config.threadContextFn);
     NcclLogger::registerHandler(
         {.contextName = "comms.utils",
          .logPrefix = config.logPrefix,
@@ -142,7 +144,7 @@ void NcclLogFormatterFactory::registerThreadContextFn(
     std::string_view name,
     std::function<int(void)> threadContextFn) {
   if (getPrefixToThreadContextFnMap().contains(std::string{name})) {
-    XLOGF(WARN, "Prefix {} re-registering thread context fn", name);
+    XLOGF(DBG1, "Prefix {} re-registering thread context fn", name);
   }
   getPrefixToThreadContextFnMap().insert_or_assign(
       std::string{name}, threadContextFn);