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?
registerFunctionRowNumberInAllBlocks(factory);
    registerFunctionNeighbor(factory);
    registerFunctionSleep(factory);
    registerFunctionSleepEachRow(factory);
    registerFunctionMaterialize(factory);
    registerFunctionIgnore(factory);
    registerFunctionIndexHint(factory);
    registerFunctionIdentity(factory);
    registerFunctionArrayJoin(factory);
    registerFunctionReplicate(factory);
    registerFunctionBar(factory);
    registerFunctionHasColumnInTable(factory);
    registerFunctionIsFinite(factory);
    registerFunctionIsInfinite(factory);
    registerFunctionIsNaN(factory);
    registerFunctionIfNotFinite(factory);
    registerFunctionThrowIf(factory);
    registerFunctionVersion(factory);
    registerFunctionBuildId(factory);
    registerFunctionUptime(factory);
    registerFunctionTimezone(factory);
    registerFunctionTimezoneOf(factory);
    registerFunctionRunningAccumulate(factory);
    registerFunctionRunningDifference(factory);
    registerFunctionRunningDifferenceStartingWithFirstValue(factory);
    registerFunctionRunningConcurrency(factory);
    registerFunctionFinalizeAggregation(factory);
    registerFunctionToLowCardinality(factory);
    registerFunctionLowCardinalityIndices(factory);
    registerFunctionLowCardinalityKeys(factory);