Fix global log level 'excess' mapping to LOG_INFO

[MrPaulAR]

SetLogLevel(const char* newLevel) is the legacy global setter, used when the API/UI is given a bare level with no level:channel targeting (SetLogLevelComplex() falls through to it when the input contains no :).

Its excess branch sets LOG_INFO instead of LOG_EXCESSIVE:

} else if (!strcmp(newLevel, "excess")) {
    FPPLogger::INSTANCE.SetAllLevel(LOG_INFO);
}

LOG_EXCESSIVE exists and is used by the per-channel path - FPPLogger::SetLevel(name, level) maps "excess" -> LOG_EXCESSIVE - so this looks like a copy/paste slip in the global variant.

Effect: POST /api/fppd/log/level/excess (and the UI log-level control) silently sets info, and additionally downgrades every channel already at debug/excess down to info - the opposite of what the caller asked for, and particularly unhelpful when the point is to gather excess detail.

Fix: use LOG_EXCESSIVE.

Repro: POST /api/fppd/log/level/excess then GET /api/fppd/log - no channel reports excess.