Update llvm to 18.1.2, lower windows to win-2019

Author: sunshaoce

.github/actions/install_llvm/action.yml

@@ -6,7 +6,7 @@ inputs:
     default: 'llvm/llvm-project'
   ref:
     description: 'The llvm-project branch, tag or SHA to checkout.'
-    default: 'llvmorg-16.0.6'
+    default: 'llvmorg-18.1.2'
   path:
     description: 'Relative path under $GITHUB_WORKSPACE to place the repository'
     default: './llvm-project'

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ on:
 jobs:
   build_and_test:
     name: Build LLDB-MI and run the testsuite
-    runs-on: windows-latest
+    runs-on: windows-2019
     steps:
       - name: Check out the repository
         uses: actions/checkout@v3.5.0