Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
void registerFunctionLowCardinalityIndices(FunctionFactory &);
void registerFunctionLowCardinalityKeys(FunctionFactory &);
void registerFunctionsIn(FunctionFactory &);
void registerFunctionJoinGet(FunctionFactory &);
void registerFunctionFilesystem(FunctionFactory &);
void registerFunctionEvalMLMethod(FunctionFactory &);
void registerFunctionBasename(FunctionFactory &);
void registerFunctionTransform(FunctionFactory &);
void registerFunctionGetMacro(FunctionFactory &);
void registerFunctionGetScalar(FunctionFactory &);
void registerFunctionGetSetting(FunctionFactory &);
void registerFunctionIsConstant(FunctionFactory &);
void registerFunctionIsDecimalOverflow(FunctionFactory &);
void registerFunctionCountDigits(FunctionFactory &);
void registerFunctionGlobalVariable(FunctionFactory &);
void registerFunctionHasThreadFuzzer(FunctionFactory &);
void registerFunctionInitializeAggregation(FunctionFactory &);
void registerFunctionErrorCodeToName(FunctionFactory &);
void registerFunctionTcpPort(FunctionFactory &);
void registerFunctionByteSize(FunctionFactory &);
void registerFunctionFile(FunctionFactory & factory);
void registerFunctionConnectionId(FunctionFactory & factory);
void registerFunctionPartitionId(FunctionFactory & factory);
void registerFunctionIsIPAddressContainedIn(FunctionFactory &);
void registerFunctionQueryID(FunctionFactory & factory);
void registerFunctionInitialQueryID(FunctionFactory & factory);
#if USE_ICU
void registerFunctionConvertCharset(FunctionFactory &);
#endif
void registerFunctionsMiscellaneous(FunctionFactory & factory)