Add new DeploymentBranchPolicies endpoints

[Ismael-Moreno]

This PR adds all the endpoints from deployment-branch-policies: https://docs.github.com/en/rest/deployments/branch-policies?apiVersion=2022-11-28#about-deployment-branch-policies

Fixes: #2610.

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[gmlewis]

Thank you, @Ismael-Moreno !
Please make sure to run gofmt on your source files.
Also, please make sure to not use force-push for your upcoming commit(s), since we always use squash-and-merge in this repo. See CONTRIBUTING.md for more info.

[gmlewis]

Thank you, @Ismael-Moreno !
One minor nit, please, then we will be ready for a second LGTM+Approval from any other contributor to this repo before merging.

[gmlewis]

Also, please make sure all unit tests pass locally before pushing the next commit.

[Ismael-Moreno]

This last one pass the three checks shown in the Contributing guide:
go generate github.com/google/go-github/...
go test github.com/google/go-github/...
go vet github.com/google/go-github/...
Please tell me if there is any other tests I'm missing, thank you for your patience.

[gmlewis]

Thank you, @Ismael-Moreno !
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.

[codecov]

Codecov Report

Merging #2621 (5f0b24e) into master (838d223) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2621      +/-   ##
==========================================
+ Coverage   98.02%   98.03%   +0.01%     
==========================================
  Files         129      130       +1     
  Lines       11084    11144      +60     
==========================================
+ Hits        10865    10925      +60     
  Misses        150      150              
  Partials       69       69              

Impacted Files	Coverage Δ
github/repos_deployment_branch_policies.go	100.00% <100.00%> (ø)

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[Parker77]

LGTM!

[gmlewis]

Thank you, @Parker77 !
Merging.

[gmlewis]

Sorry, @Ismael-Moreno - but as I was about to merge, I noticed that DeploymentBranchPolicies is singular Deployment whereas the new filenames are ..._deployments_branch_... .

Could you please rename the new files to use a singular ..._deployment_... please?

[gmlewis]

Thank you, @Ismael-Moreno !
Merging.