Function generate_import_block 

pub fn generate_import_block<'a>(
    exprs: impl IntoIterator<Item = &'a CodecExpr>,
) -> Result<String, Vec<DiagnosticKind>>

Generate the import block for a set of expressions.

Always starts with import * as r from 'rkyv-js';, followed by named imports grouped by module and sorted by module specifier (exports sorted within each statement).

The same export name imported from two different modules is reported as DiagnosticKind::ImportConflict.