[trace] Add SBTraceCursor bindings

[trace] Add SBTraceCursor bindings

Add bindings for the `TraceCursor` to allow for programatic traversal of
traces.
This diff adds bindings for all public `TraceCursor` methods except
`GetHwClock` and also adds `SBTrace::CreateNewCursor`. A new unittest
has been added to TestTraceLoad.py that uses the new `SBTraceCursor` API
to test that the sequential and random access APIs of the `TraceCursor`
are equivalent.

This diff depends on D130925.

Test Plan:
`ninja lldb-dotest && ./bin/lldb-dotest -p TestTraceLoad`

Differential Revision: https://reviews.llvm.org/D130930