solc-json-interface: do not unconditionally skip serialization of custom keys (#337)

The data structure can be used to build the JSON input for `resolc` too.
In that case serializing of provided custom options should not be
dismissed.

Makes the memory settings struct more modular as a drive-by.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/resolc/src/lib.rs

@@ -229,7 +229,7 @@ pub fn standard_json<T: Compiler>(
         revive_llvm_context::OptimizerSettings::try_from(&solc_input.settings.optimizer)?;
 
     let polkavm_settings = solc_input.settings.polkavm.unwrap_or_default();
-    debug_config.emit_debug_info = polkavm_settings.debug_information;
+    debug_config.emit_debug_info = polkavm_settings.debug_information.unwrap_or_default();
 
     let include_metadata_hash = match solc_input.settings.metadata {
         Some(ref metadata) => metadata.bytecode_hash != Some(MetadataHash::None),
@@ -265,7 +265,9 @@ pub fn standard_json<T: Compiler>(
             include_metadata_hash,
             debug_config,
             llvm_arguments,
-            polkavm_settings.memory_config,
+            polkavm_settings
+                .memory_config
+                .unwrap_or_else(SolcStandardJsonInputSettingsPolkaVMMemory::default),
         )?;
         build.write_to_standard_json(&mut solc_output, &solc_version)?;
     }

crates/resolc/src/resolc/main.rs

@@ -142,14 +142,10 @@ fn main_inner() -> anyhow::Result<()> {
         None => true,
     };
 
-    let mut memory_config =
-        revive_solc_json_interface::SolcStandardJsonInputSettingsPolkaVMMemory::default();
-    if let Some(heap_size) = arguments.heap_size {
-        memory_config.heap_size = heap_size
-    }
-    if let Some(stack_size) = arguments.stack_size {
-        memory_config.stack_size = stack_size
-    }
+    let memory_config = revive_solc_json_interface::SolcStandardJsonInputSettingsPolkaVMMemory::new(
+        arguments.heap_size,
+        arguments.stack_size,
+    );
 
     let build = if arguments.yul {
         resolc::yul(