Replace clang-format, clang-tidy, etc. with clangd

[fbaeuerlein]

Possible settings.json configuration

"clangd.semanticHighlighting": true,
"clangd.checkUpdates": true,
"clangd.arguments": [
    "-clang-tidy",
    "--compile-commands-dir=${workspaceFolder}/build",        
    "--header-insertion=iwyu",
    // "--suggest-missing-includes", 
    "-log=verbose"
]

Seems not to work currently together with clang-tidy. No errors are displayed (e.g. nullptr deref). Maybe wait for update of ext or vscode.