feat: improve metrics of yurthub component

[rambohe-ch]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line: /kind bug /kind documentation /kind enhancement /kind good-first-issue /kind feature /kind question /kind design /sig ai /sig iot /sig network /sig storage

/kind enhancement

What this PR does / why we need it:

1. use entire user agent for cloud working mode, so requests that posted by controller clients of each yurt-manager can be monitored in yurthub metrics
2. wrap response in order to recored the traffic for any resource requests instead only for requests that be cached.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.33333% with 22 lines in your changes missing coverage. Please review.

Project coverage is 56.14%. Comparing base (3713163) to head (81de8b3). Report is 10 commits behind head on master.

Files	Patch %	Lines
pkg/yurthub/util/util.go	0.00%	21 Missing :warning:
pkg/yurthub/proxy/remote/loadbalancer.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2091 +/- ## ========================================== + Coverage 56.09% 56.14% +0.05% ========================================== Files 186 186 Lines 18092 18054 -38 ========================================== - Hits 10149 10137 -12 + Misses 6910 6885 -25 + Partials 1033 1032 -1 ``` | [Flag](https://app.codecov.io/gh/openyurtio/openyurt/pull/2091/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/openyurtio/openyurt/pull/2091/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio) | `56.14% <33.33%> (+0.05%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[luc99hen]

/approve

[luc99hen]

/lgtm