Separate compilation and linker phases (#376)

Separate between compilation and linker phases to allow deploy time
linking and back-porting era compiler changes to fix #91. Unlinked
contract binaries (caused by missing libraries or missing factory
dependencies in turn) are emitted as raw ELF object.

Few drive by fixes:
- #98
- A compiler panic on missing libraries definitions.
- Fixes some incosistent type forwarding in JSON output (empty string
vs. null object).
- Remove the unused fallback for size optimization setting.
- Remove the broken `--lvm-ir`  mode.
- CI workflow fixes.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Signed-off-by: xermicus <bigcyrill@hotmail.com>
Signed-off-by: xermicus <cyrill@parity.io>

crates/resolc/src/tests/data/standard_json/yul_solc.json

@@ -0,0 +1,29 @@
+{
+  "language": "Yul",
+  "sources": {
+    "Test": {
+      "content": "object \"Return\" { code { { return(0, 0) } } object \"Return_deployed\" { code { { return(0, 0) } } } }"
+    }
+  },
+  "settings": {
+    "optimizer": {
+      "enabled": true
+    },
+    "metadata": {
+      "useLiteralContent": true
+    },
+    "outputSelection": {
+      "*": {
+        "": [
+          "ast"
+        ],
+        "*": [
+          "abi",
+          "evm.methodIdentifiers",
+          "evm.bytecode"
+        ]
+      }
+    },
+    "libraries": {}
+  }
+}