[UR] Lazily initialize GlobalAdapter (#21490)
**Problem**
`ur_win_proxy_loader` loads L0 adapter DLL in its `DLLMain`. Global
variables are initialized during DLL loading and so is `GlobalAdapter` -
which tries to initialize L0 driver (`zeInit`). `zeInit` may spawn
threads and it's illegal to spawn threads directly or indirectly from
`DLLMain`.
This is causing deadlock with some L0 driver versions.
**Proposed Solution**
Lazily initialize `GlobalAdapter`, just like what we do on Linux.
