[User.Sql] publish password to Connection Secret

[ytsarev]

Description of your changes

To effectively use this MR within higher level abstractions like https://github.com/upbound/configuration-gcp-database and eventually https://github.com/upbound/platform-ref-gcp/ we need a reliable way to expose SQL User password through the connection secret

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

diff --git a/examples/sql/user.yaml b/examples/sql/user.yaml
index dbe3e7f9..987fb3a7 100644
--- a/examples/sql/user.yaml
+++ b/examples/sql/user.yaml
@@ -48,7 +48,7 @@ metadata:
   labels:
     testing.upbound.io/example-name: example_instance
   # ${Rand...} is not valid YAML and is used with automated testing
-  name: example-instance-${Rand.RFC1123Subdomain}
+  name: example-instance-yury-test
 spec:
   forProvider:
     region: "us-central1"


k apply -f examples/sql/user.yaml
...
 k get -f examples/sql/user.yaml
NAME                                   READY   SYNCED   EXTERNAL-NAME   AGE
user.sql.gcp.upbound.io/example-user   True    True     example-user    16m

NAME                      TYPE     DATA   AGE
secret/example-sql-user   Opaque   1      16m

NAME                                                             READY   SYNCED   EXTERNAL-NAME                AGE
databaseinstance.sql.gcp.upbound.io/example-instance-yury-test   True    True     example-instance-yury-test   16m

k view-secret -n upbound-system example-sql-db-user-secret
Multiple sub keys found. Specify another argument, one of:
-> attribute.password
-> password

 k view-secret -n upbound-system example-sql-db-user-secret password
changeme%

Plus uptest below

[ytsarev]

/test-examples="examples/sql/user.yaml"

[turkenf]

Thank you @ytsarev, LGTM.

[ytsarev]

I do not have access rights to this repo. @turkenf please feel free to merge it in. Alternatively, @jeanduplessis , feel free to give me merge access rights :D