[FaqGen] Fix the metrics parse and statistics for benchmark

[wangkl2]

Description

Fix the metrics parse and statistics for FaqGen benchmark:

• Switch from json to data param to send client request for FaqGen benchmark to fit the FormData input_type.
• Fix the input length statistics, to avoid negative numbers of Input Tokens and Input Tokens per Second.
• Fix the output length statistics by implementing the extraction of all generated texts from streaming output, to avoid extremely large values of Output Tokens and Output Tokens per Second.
• Update the default input prompt and set Top K=1 in sampling for faqgen, as the original default prompt does not provide any valid details for faq generation.

Issues

#189

Type of change

List the type of change like below. Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Dependencies

n/a

Tests

Benchmark on faqgenfixed.

[lkk12014402]

LGTM