perf(command): user grant pre-condition check using the search table (#8230)

# Which Problems Are Solved

Imporve the performance of user grant addition, especially for import.

# How the Problems Are Solved

Use the search table to query for the project grant state. 
This could easily be done by making the search used in
`checkProjectGrantPreCondition` reusable.

# Additional Changes

Chanded event declerations to `const` in the
`internal/repository/project` package.

# Additional Context

- Performance improvements for import are evaluated and acted upon
internally at the moment

---------

Co-authored-by: adlerhurst <silvan.reusser@gmail.com>
Co-authored-by: Livio Spring <livio.a@gmail.com>

proto/zitadel/feature/v2beta/feature.proto

@@ -59,4 +59,5 @@ enum ImprovedPerformance {
   // correctnes of data.
   IMPROVED_PERFORMANCE_PROJECT_GRANT = 2;
   IMPROVED_PERFORMANCE_PROJECT = 3;
+  IMPROVED_PERFORMANCE_USER_GRANT = 4;
 }