Add a regression test to `rust-wasm-test` for underscore in table names

[cloutiertyler]

#[spacetimedb::table(name = _LegacyPrivate)]
pub struct LegacyPrivate {
    sensitive: String
}

[kim]

https://github.com/clockworklabs/SpacetimeDB/pull/1689#issuecomment-2345422671