Data breakpoints in OpenDebugAD7

[calgagi]

This PR implements DataBreakpointInfo and SetDataBreakpoints for OpenDebugAD7's debug session as a part of the Debug Adapter Protocol (DAP).

Notes:

1. Caches IDebugProperty2s in VariableManager for lookup by name/VariableReference later to be used for data breakpoints. We can query for IDebugProperty160 on these to use GetDataBreakpointInfo160.
2. Makes AD7Property.EnumChildren support filtering with the child's name (specified here with pszNameFilter)
3. Supports BPLT_DATA_STRING in AD7BreakpointRequest (returns the proper address/size).
4. The DataId passed to/from VS Code as part of both DAP functions is "{address},{size}"

Potential problems/things to improve:

1. If users have too many data breakpoints, then we receive an exception that GDB can't continue the debuggee process and we display a very mysterious error message: "Debugger was unable to continue the process."
2. If a variable size is too big to set a data breakpoint on, then we simply don't display the "Break When Value Changes" context menu item. It might be worthwhile in the future to say why it doesn't display.
3. Add test :)

[gregg-miskelly]

Otherwise LGTM