* implement functions to append/get metadata and set/get status code
* сhanged behavior to return nil instead of empty metadata for getResponseMetadata()
* сhanged work with HTTP headers to use direct array assignment instead of for-range
* fix linters
* fix meter handler
* fix uninitialized response metadata for incoming context
* removed a useless test
* metrics handler has been fixed to work with compressed data
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Co-authored-by: Gorbunov Kirill Andreevich <kgorbunov@mtsbank.ru>
Reviewed-on: #188
Co-authored-by: Кирилл Горбунов <kirya_gorbunov_2015@mail.ru>
Co-committed-by: Кирилл Горбунов <kirya_gorbunov_2015@mail.ru>
