`DebugSession` client path conversion should work in web extensions

[idavis]

Writing cross-platform and web cabable extensions, one is unable to call DebugSession::setDebuggerPathFormat and rely on the conversion methods for client and debugger path conversion.

Expected behavior

DebugSession::convertClientPathToDebugger and DebugSession::convertDebuggerPathToClient should work in desktop and web extensions.

Current behavior

Calling DebugSession::convertClientPathToDebugger or DebugSession::convertDebuggerPathToClient throws an exception process is not defined when DebugSession::path2uri and DebugSession::uri2path are called due to a dependency on process.platform from node.