Support performance benchmarking using Google benchmark

[swebb2066]

Sample output using gcc 11:
Running bin/gbenchmarks
Run on (8 X 2219.48 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x4)
L1 Instruction 32 KiB (x4)
L2 Unified 256 KiB (x4)
L3 Unified 6144 KiB (x1)
Load Average: 0.39, 0.35, 0.21

Benchmark	Time	CPU	Iterations
Testing disabled logging request/min_warmup_time:0.100	3.47 ns	3.47 ns	202404072
Testing disabled logging request/threads:6	0.969 ns	5.81 ns	120580806
Logging static string	259 ns	259 ns	2700483
Logging static string with printf	276 ns	276 ns	2501396
Logging int value with printf	328 ns	328 ns	2139323
Logging int value with printf/threads:6	341 ns	1867 ns	372012
Logging int+float with printf	633 ns	633 ns	1126516
Logging int+float with printf/threads:6	423 ns	2418 ns	291102
Logging int value with streams	306 ns	306 ns	2290726
Logging int value with streams/threads:6	349 ns	1920 ns	373212
Logging int+float with streams	746 ns	746 ns	934805
Logging int+float with streams/threads:6	410 ns	2397 ns	281964
NoFormat pattern: %m%n	300 ns	300 ns	2230819
DateOnly pattern: [%d] %m%n	304 ns	304 ns	2227857
DateClassLevel pattern: [%d] [%c] [%p] %m%n	300 ns	300 ns	2228585
Logging int value with streams to AsyncAppender	303 ns	302 ns	2269183
Logging int value with streams to AsyncAppender/threads:6	474 ns	2521 ns	372276