Support breakpoints for specific threads

[eronnen]

Currently it's achievable by setting a breakpoint condition like "(int)thread.gettid() == 5", but debuggers like LLDB support directly specifying thread id(s) for a breakpoint, which is much faster then evaluating the condition expression every time the breakpoint hits:

Syntax: breakpoint modify <cmd-options> [<breakpt-id | breakpt-id-list>]

 -t <thread-id> ( --thread-id <thread-id> )
            The breakpoint stops only for the thread whose TID matches this argument.  The token
            'current' resolves to the current thread's ID.

[DrSergei]

I am also interested in this feature. Looks like, we can use BreakpointMode to identify a thread when setting breakpoint. However, there is a problem, when I try to send CapabilitiesEvent with new breakpointModes, the VSCode ignore new values (registerBreakpointModes called once in initialize request). Does the VSCode team intend to improve the behavior of CapabilitiesEvent?