[exporter/chronicleexporter]: Optimize getRawField when field is "body"

[jsirianni]

Proposed Change

getRawField is called three times for every log record. One of the calls is for reading the "field to send" value. Generally, "field to send" will be body. Body can be either a string or a map.

If field is body, we can read the underlying string or map and return it. No need to use an expensive OTTL expression.

Before

Benchmark_getRawField/String_body-32         	  522542	     21758 ns/op
Benchmark_getRawField/Empty_body-32          	  566030	     23555 ns/op
Benchmark_getRawField/Map_body-32            	  529818	     26545 ns/op
Benchmark_getRawField/Map_body_field-32      	  427791	     29865 ns/op
Benchmark_getRawField/Map_body_field_missing-32         	  477262	     26456 ns/op
Benchmark_getRawField/String_attribute-32               	  480273	     25780 ns/op
Benchmark_getRawField/String_attribute_missing-32       	  477435	     25497 ns/op

After

Benchmark_getRawField/String_body-32         	337642196	         3.273 ns/op
Benchmark_getRawField/Empty_body-32          	416621745	         2.768 ns/op
Benchmark_getRawField/Map_body-32            	 1249923	       947.6 ns/op
Benchmark_getRawField/Map_body_field-32      	   35430	     32555 ns/op
Benchmark_getRawField/Map_body_field_missing-32         	   38889	     34986 ns/op
Benchmark_getRawField/Attribute_log_type-32             	 5498604	       233.0 ns/op
Benchmark_getRawField/Attribute_log_type_missing-32     	 7433708	       164.2 ns/op
Benchmark_getRawField/Attribute_chronicle_log_type-32   	 7790766	       218.1 ns/op
Benchmark_getRawField/Attribute_chronicle_namespace-32  	 4046871	       284.6 ns/op

Benchmarks for string body and map body have almost no costs now.

The tests introduced in #1966 should prove that the output is the same.

Checklist

• Changes are tested
• CI has passed

[dpaasman00]

Looks great