Fuzzing corpus for ParseMetric.

promql/fuzz-data/ParseMetric/corpus/exposition_formats_0

+# HELP api_http_request_count The total number of HTTP requests.
+# TYPE api_http_request_count counter
+http_request_count{method="post",code="200"} 1027 1395066363000

promql/fuzz-data/ParseMetric/corpus/exposition_formats_1

+msdos_file_access_time_ms{path="C:\\DIR\\FILE.TXT",error="Cannot find file:\n\"FILE.TXT\""} 1.234e3

promql/fuzz-data/ParseMetric/corpus/exposition_formats_2

+metric_without_timestamp_and_labels 12.47

promql/fuzz-data/ParseMetric/corpus/exposition_formats_3

+something_weird{problem="division by zero"} +Inf -3982045

promql/fuzz-data/ParseMetric/corpus/exposition_formats_4

+http_request_duration_seconds_bucket{le="+Inf"} 144320