improve restmapper for gateway resource

[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:

because plural of gateway is gateways instead of gatewaies in raven, so we need to deal with gateway resource specially in restmapper of yurthub component.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.1% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 55.56%. Comparing base (e4740ba) to head (342f62c). Report is 2 commits behind head on master.

Files	Patch %	Lines
pkg/yurthub/kubernetes/meta/restmapper.go	83.33%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2054 +/- ## ========================================== - Coverage 55.63% 55.56% -0.07% ========================================== Files 186 186 Lines 18079 18089 +10 ========================================== - Hits 10058 10052 -6 - Misses 6998 7011 +13 - Partials 1023 1026 +3 ``` | [Flag](https://app.codecov.io/gh/openyurtio/openyurt/pull/2054/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/2054/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio) | `55.56% <83.33%> (-0.07%)` | :arrow_down: | 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.

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