[lldb] Add the word "backtrace" to bt help string (#92618)

We noticed that `apropos backtrace` did not return the `bt` alias. This change adds the 
word "backtrace" to the help for `bt`. It also updates `thread backtrace` to keep the 
language used roughly in sync.

Author: kastiglione

lldb/source/Commands/CommandObjectThread.cpp

@@ -114,8 +114,8 @@ class CommandObjectThreadBacktrace : public CommandObjectIterateOverThreads {
   CommandObjectThreadBacktrace(CommandInterpreter &interpreter)
       : CommandObjectIterateOverThreads(
             interpreter, "thread backtrace",
-            "Show thread call stacks.  Defaults to the current thread, thread "
-            "indexes can be specified as arguments.\n"
+            "Show backtraces of thread call stacks.  Defaults to the current "
+            "thread, thread indexes can be specified as arguments.\n"
             "Use the thread-index \"all\" to see all threads.\n"
             "Use the thread-index \"unique\" to see threads grouped by unique "
             "call stacks.\n"

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -828,11 +828,11 @@ void CommandInterpreter::LoadCommandDictionary() {
   std::unique_ptr<CommandObjectRegexCommand> bt_regex_cmd_up(
       new CommandObjectRegexCommand(
           *this, "_regexp-bt",
-          "Show the current thread's call stack.  Any numeric argument "
-          "displays at most that many "
-          "frames.  The argument 'all' displays all threads.  Use 'settings"
-          " set frame-format' to customize the printing of individual frames "
-          "and 'settings set thread-format' to customize the thread header.",
+          "Show backtrace of the current thread's call stack.  Any numeric "
+          "argument displays at most that many frames.  The argument 'all' "
+          "displays all threads.  Use 'settings set frame-format' to customize "
+          "the printing of individual frames and 'settings set thread-format' "
+          "to customize the thread header.",
           "bt [<digit> | all]", 0, false));
   if (bt_regex_cmd_up) {
     // accept but don't document "bt -c <number>" -- before bt was a regex