refactor: make Kargo Roles proper runtime objects

[krancour]

Follow up to #1906 and related to #1916

Kargo Roles are the one place in all of our APIs where protobuf messages might be shown directly to a user -- which is how I became aware of #1916.

While there may be some things that can be done about #1916, I recognize that protobuf field names should only matter over the wire and are, essentially, an implementation detail that really never should bleed through to the user. i.e. I don't want to get hung up on fixing #1916 to force json struct tags to look a certain go-ish way.

This sent me down the rabbit hole of trying something new, that turns out to solve a lot of problems at once...

1. I created a new rbac.kargo.akuity.io/v1alpha1 API wherein Roles are proper k8s runtime objects (although we skip the CRD generation for these, because it's not needed)

2. This drastically cleans up the RoleDatabase interface, because it now deals with rbacapi.Role objects instead of dealing directly with protobuf messages -- something it probably shouldn't have done in the first place.

3. Protobuf messages like GetRoleRequest now wrap Role messages that are generated from the Role runtime object -- i.e. we now handle this exactly as we have always handled GetStageRequest, GetPromotionRequest, etc., which have also always wrapped messages generated from runtime objects. Consistency ftw.

4. Any JSON or YAML the CLI shows to users now is more conventionally k8s-looking (fields names are lowerCamelCase instead of snake_case).

5. Last, but certainly not least, Roles being proper runtime objects eliminates all the slight of hand that was previously required to make

There are also some tiny bug fixes to revoke logic in here.

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[codecov]

Codecov Report

Attention: Patch coverage is 35.50725% with 89 lines in your changes are missing coverage. Please review.

Project coverage is 45.58%. Comparing base (c6d0a6d) to head (cde3a98).

Files	Patch %	Lines
internal/api/rbac/roles.go	75.38%	12 Missing and 4 partials ⚠️
internal/cli/cmd/get/roles.go	0.00%	15 Missing ⚠️
internal/api/list_roles_v1alpha1.go	0.00%	10 Missing ⚠️
internal/cli/cmd/create/role.go	0.00%	9 Missing ⚠️
api/rbac/v1alpha1/groupversion_info.go	0.00%	8 Missing ⚠️
internal/api/get_role_v1alpha1.go	0.00%	8 Missing ⚠️
internal/cli/cmd/delete/role.go	0.00%	5 Missing ⚠️
internal/cli/cmd/grant/grant.go	0.00%	3 Missing ⚠️
internal/cli/cmd/revoke/revoke.go	0.00%	3 Missing ⚠️
internal/kubeclient/indexer.go	0.00%	3 Missing ⚠️
... and 6 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1917      +/-   ##
==========================================
+ Coverage   45.52%   45.58%   +0.06%     
==========================================
  Files         235      235              
  Lines       15823    15793      -30     
==========================================
- Hits         7203     7199       -4     
+ Misses       8267     8240      -27     
- Partials      353      354       +1     

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[hiddeco]

👏!