[SMDLL][SMLIB] Deprecate the legacy ROS-specific SMDLL and improve SM client functions. (#4821)

This DLL was exporting legacy NT-incompatible or ROS-specific SM client
functions, that have been sinc

[SMDLL][SMLIB] Deprecate the legacy ROS-specific SMDLL and improve SM client functions. (#4821)

This DLL was exporting legacy NT-incompatible or ROS-specific SM client
functions, that have been since 10 years now (2012) replaced by the new
NT-compatible SM:

- SmConnectApiPort(): was just SmConnectToSm().

- SmCompleteSession():
The legacy SMSS used it for when a subsystem initialization was finished.
Now (NT-compatible) this function is called by subsystems **only** when a
subsystem session **terminates**: SmSessionComplete().

- SmExecuteProgram(): was just the client side of SmLoadDeferedSubSystem()
(whose server side is not implemented yet). The legacy SM "old" SmExecPgm
implementation actually was "SmLoadDeferedSubSystem"...

- SmLookupSubsystem(): is a utility-only function to read any registry value
inside "Session Manager\SubSystems".

Move SMDLL's readme into SMLIB and update its contents.

Collect some residual useful functions into smutils.c (and moved in SMLIB,
though not compiled yet):
- SmExecuteProgram(), now implemented as a wrapper around SmExecPgm();
- SmLookupSubsystem(), described above;
- SmQueryInformation(), that retrieves a list of currently-running subsystems.

[SMLIB] Validate SbApiPortName's length in SmConnectToSm().
Fix CommandLine length validation in SmStartCsr().

Add documentation (+ SAL annotations) to the NT-compatible SMSS client functions.

smmsg.h: Add both Win32 and Win64 struct sizes C_ASSERTs for those whose size
change between these two processor architecture sizes.

[SMLIB] Introduce SmSendMsgToSm() as helper to send data into the SM LPC port.
+ Make the other API functions use it.

It should be observed that in Vista+, both functions SmConnectToSm() and this
new SmSendMsgToSm() are exported by NTDLL under the names RtlConnectToSm()
and RtlSendMsgToSm() (and use the same signature).
See: https://www.geoffchappell.com/studies/windows/win32/ntdll/history/names60.htm

[NTDLL] Correctly stub RtlConnectToSm() and RtlSendMsgToSm().
[NTDLL_VISTA] Link to SMLIB and simply export RtlConnectToSm() and RtlSendMsgToSm().

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