Implement column alias's in C# and Rust modules

[cloutiertyler]

We'd like to be able to do something like this:

// We're using this table as a singleton, so in this table
// there only be one element where the `id` is 0.
[Table(Name = "config", Public = true)]
public partial struct Config
{
    [PrimaryKey]
    [Column(Name = "id")]
    public uint Id;
    [Column(Name = "world_size")]
    public ulong WorldSize;
}

// We're using this table as a singleton, so in this table
// there only be one element where the `id` is 0.
#[spacetimedb::table(name = config, public)]
pub struct Config {
    #[primary_key]
    pub id: u32,
    #[column(name = "foobar")]
    pub foobar: u64,
}

Exactly spelling not proposed. Needs design work. This is a common feature in ORMs:

https://orm.drizzle.team/docs/sql-schema-declaration#tables-and-columns-declaration

[RReverser]

FWIW we already use the standard [DataMember(Name = "...")] attribute in autogenerated C# code to preserve column names for JSON representation (which was important for BitCraft):

SpacetimeDB/crates/cli/tests/snapshots/codegen__codegen_csharp.snap

Lines 110 to 119 in 729dbb1

	[SpacetimeDB.Type]
	[DataContract]
	public partial class Player : IDatabaseRow
	{
	[DataMember(Name = "identity")]
	public SpacetimeDB.Identity Identity;
	[DataMember(Name = "player_id")]
	public ulong PlayerId;
	[DataMember(Name = "name")]
	public string Name;

In C# it might make sense to reuse the same attribute for server-side as well, instead of introducing a separate one, since DataMember can be reused by various serializers.