Support external (i.e. user-defined) trace annotations (#195)

* Support external (i.e. user-defined) trace annotations

- tweaked the python examples to be more balanced
- updated the user-api example to conform to user API changes
- moved the get/set for State and ThreadState to state.{hpp,cpp}
- introduced user-provided trace annotations
- added perfetto python category
- moved coverage impl files around
- created enumerations for mapping category enums to category types
- created enumerations for mapping annotation type enums to annotation values
- moved tracing::add_perfetto_annotations to tracing/annotation.hpp
- utility make_index_sequence_range
- libomnitrace-dl: omnitrace_push_category_region
- libomnitrace-dl: omnitrace_pop_category_region
- libomnitrace-user: omnitrace_user_push_annotated_region
- libomnitrace-user: omnitrace_user_pop_annotated_region
- libpyomnitrace: support extra annotations via annotate_trace config value
  - filename
  - line
  - last attempted instr in bytecode (lasti)
  - argcount
  - num local variables
  - stacksize
- omnitrace-python: -a / --annotate-traces option

* tweak ubuntu-focal workflow

* Fix installation of omnitrace-user headers

* ubuntu-focal-codecov workflow update

- Install texinfo

* Update timemory submodule

source/lib/omnitrace/library/config.cpp

@@ -2051,25 +2051,4 @@ get_tmp_file(std::string _basename, std::string _ext)
     return _existing_files.at(_fname);
 }
 }  // namespace config
-
-State&
-get_state()
-{
-    static State _v{ State::PreInit };
-    return _v;
-}
-
-State
-set_state(State _n)
-{
-    auto _o = get_state();
-    OMNITRACE_CONDITIONAL_PRINT_F(get_debug_init(), "Setting state :: %s -> %s\n",
-                                  std::to_string(_o).c_str(), std::to_string(_n).c_str());
-    // state should always be increased, not decreased
-    OMNITRACE_CI_BASIC_THROW(_n < _o,
-                             "State is being assigned to a lesser value :: %s -> %s",
-                             std::to_string(_o).c_str(), std::to_string(_n).c_str());
-    get_state() = _n;
-    return _o;
-}
 }  // namespace omnitrace