thrift_proxy: Add zone response metrics to thrift upstream requests

[fishcakez]

Commit Message: Add zone response metrics to thrift upstream requests
Additional Description: Add response type/reply type counters and request time per zone pair upstream metrics in the same format as http zone metrics.
Risk Level: low
Testing: unit tests and local deployment
Docs Changes: N/A
Release Notes: Yes, added metrics.
Platform Specific Features: N/A

[rgs1]

Looks good once we get the formatting passing, thanks!

[rgs1]

@fishcakez almost there, small drop in coverage:

Per-extension coverage failed:
Code coverage for source/extensions/filters/network/thrift_proxy/router is lower than limit of 96.4 (96.2)
##[error]Bash exited with code '1'.

https://dev.azure.com/cncf/envoy/_build/results?buildId=91332&view=logs&jobId=bbe4b42d-86e6-5e9c-8a0b-fea01d818a24&j=bbe4b42d-86e6-5e9c-8a0b-fea01d818a24&t=e00c5a13-c6dc-5e9a-6104-69976170e881

https://storage.googleapis.com/envoy-pr/ca0196f/coverage/source/extensions/filters/network/thrift_proxy/router/index.html

[fishcakez]

small drop in coverage

From the output you shared the drop is due to adding some empty lines, which get reported as 0 counts, so I just deleted 4 of the ones I introduced.

[davinci26]

Assigning myself for final review after the thrift folks approve.

[rgs1]

Looks great, thanks!

Over to @davinci26 for final pass & merge.

[davinci26]

Thanks, LGTM