Add resources for managing OCI auth backends

[F21]

Community Note

• Please vote on this pull request by adding a 👍 reaction to the original pull request comment to help the community and maintainers prioritize this request
• Please do not leave "+1" comments, they generate extra noise for pull request followers and do not help prioritize the request

Closes #1758

Release note for CHANGELOG:

Add OCI (Oracle Cloud Infrastructure) Auth Backend resources: `vault_oci_auth_backend_config` and `vault_oci_auth_backend_role`

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccXXX'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test -run=TestAccXXX -timeout 30m ./...
?       github.com/hashicorp/terraform-provider-vault   [no test files]
?       github.com/hashicorp/terraform-provider-vault/cmd/coverage      [no test files]
?       github.com/hashicorp/terraform-provider-vault/cmd/generate      [no test files]
?       github.com/hashicorp/terraform-provider-vault/generated [no test files]
ok      github.com/hashicorp/terraform-provider-vault/codegen   0.005s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/generated/datasources/transform/decode    0.015s [no tests to run]
?       github.com/hashicorp/terraform-provider-vault/helper    [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/consts   [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/identity/group   [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/identity/mfa     [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/pki      [no test files]
?       github.com/hashicorp/terraform-provider-vault/schema    [no test files]
ok      github.com/hashicorp/terraform-provider-vault/generated/datasources/transform/encode    0.023s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/generated/resources/transform/alphabet    0.018s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/generated/resources/transform/role        0.017s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/generated/resources/transform/template    0.023s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/generated/resources/transform/transformation      0.022s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/internal/identity/entity  0.022s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/internal/provider 0.021s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/testutil  0.009s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/util      0.010s [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/vault     0.020s [no tests to run]
...

[F21]

Any chance this can be reviewed?