[Rust] Extend view table accessors with count (#4638)

# Description of Changes

Adds `count` to rust's procedural view API.

This API already existed in C# and typescript. This patch just adds
tests for those module languages.

We were already tracking reads for `count`, and so all this patch does
is add the new rust module bindings.

# API and ABI breaking changes

None

# Expected complexity level and risk

1

# Testing

Smoketests for rust, C#, and typescript.

Author: joshua-spacetime

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#FFI.verified.cs

@@ -294,6 +294,12 @@ SpacetimeDB.BSATN.ITypeRegistrar registrar
 
         public static SpacetimeDB.Internal.RawScheduleDefV10? MakeScheduleDesc() => null;
 
+        /// <summary>
+        /// Returns the number of rows in this table.
+        ///
+        /// This reads datastore metadata, so it runs in constant time.
+        /// It also takes into account modifications by the current transaction.
+        /// </summary>
         public ulong Count =>
             global::SpacetimeDB.Internal.ITableView<DemoTable, global::DemoTable>.DoCount();
 
@@ -391,6 +397,12 @@ public sealed class DemoTableReadOnly
         internal DemoTableReadOnly()
             : base("DemoTable") { }
 
+        /// <summary>
+        /// Returns the number of rows in this table.
+        ///
+        /// This reads datastore metadata, so it runs in constant time.
+        /// It also takes into account modifications by the current transaction.
+        /// </summary>
         public ulong Count => DoCount();
 
         public sealed class IdIndex