Adds GatewayClass Finalizer

[danehans]

Fixes #358

Signed-off-by: danehans daneyonhansen@gmail.com

[danehans]

Codecov is failing to upload:

[2022-09-12T16:21:19.242Z] ['info'] Pinging Codecov: https://codecov.io/upload/v4?package=github-action-2.1.0-uploader-0.3.1&token=*******&branch=issue_358&build=3038860468&build_url=https%3A%2F%2Fgithub.com%2Fenvoyproxy%2Fgateway%2Factions%2Fruns%2F3038860468&commit=5227bcf618e102174c4eea7f68a62f9c1fcdc3d1&job=Build+and+Test&pr=373&service=github-actions&slug=envoyproxy%2Fgateway&name=codecov-envoy-gateway&tag=&flags=&parent=
[2022-09-12T16:21:19.242Z] ['verbose'] Passed token was 0 characters long
[2022-09-12T16:21:19.242Z] ['verbose'] https://codecov.io/upload/v4?package=github-action-2.1.0-uploader-0.3.1&branch=issue_358&build=30388[60](https://github.com/envoyproxy/gateway/actions/runs/3038860468/jobs/4893149913#step:5:61)468&build_url=https%3A%2F%2Fgithub.com%2Fenvoyproxy%2Fgateway%2Factions%2Fruns%2F3038860468&commit=5227bcf[61](https://github.com/envoyproxy/gateway/actions/runs/3038860468/jobs/4893149913#step:5:62)8e102174c4eea7f68a62f9c1fcdc3d1&job=Build+and+Test&pr=373&service=github-actions&slug=envoyproxy%2Fgateway&name=codecov-envoy-gateway&tag=&flags=&parent=
        Content-Type: 'text/plain'
        Content-Encoding: 'gzip'
        X-Reduced-Redundancy: 'false'
[2022-09-12T16:21:19.606Z] ['error'] There was an error running the uploader: Error uploading to [https://codecov.io:](https://codecov.io/) Error: There was an error fetching the storage URL during POST: 404 - {'detail': ErrorDetail(string='Unable to locate build via Github Actions API. Please upload with the Codecov repository upload token to resolve issue.', code='not_found')}
[2022-09-12T16:21:19.607Z] ['verbose'] The error stack is: Error: Error uploading to [https://codecov.io:](https://codecov.io/) Error: There was an error fetching the storage URL during POST: 404 - {'detail': ErrorDetail(string='Unable to locate build via Github Actions API. Please upload with the Codecov repository upload token to resolve issue.', code='not_found')}
    at main (/snapshot/repo/dist/src/index.js)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
[2022-09-12T16:21:19.607Z] ['verbose'] End of uploader: 4[68](https://github.com/envoyproxy/gateway/actions/runs/3038860468/jobs/4893149913#step:5:69) milliseconds
Error: Codecov: Failed to properly upload: The process '/home/runner/work/_actions/codecov/codecov-action/v2/dist/codecov' failed with exit code 255

Rerunning the failed job.

[codecov-commenter]

Codecov Report

Merging #373 (7c63c72) into main (ac5ea77) will increase coverage by 0.20%.
The diff coverage is 78.72%.

@@            Coverage Diff             @@
##             main     #373      +/-   ##
==========================================
+ Coverage   60.98%   61.18%   +0.20%     
==========================================
  Files          35       36       +1     
  Lines        3637     3682      +45     
==========================================
+ Hits         2218     2253      +35     
- Misses       1302     1309       +7     
- Partials      117      120       +3     

Impacted Files	Coverage Δ
internal/provider/kubernetes/gatewayclass.go	65.04% <57.14%> (-3.34%)	⬇️
internal/provider/kubernetes/gateway.go	69.47% <74.07%> (+0.57%)	⬆️
internal/utils/slice/slice.go	100.00% <100.00%> (ø)
internal/gatewayapi/runner/runner.go	68.23% <0.00%> (+3.52%)	⬆️

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