[debugging.utility] Clarify wording in notes

The previous wording in the notes in `breakpoint` and `is_debugger_present`
read as statements of fact about the implementation-defined behaviour.
The statements are actually ones of intent.

The specific claim in `breakpoint` that the debugger resumes execution of the program
as if the function was not invoked is confusing considering that the debugger may effect
side-effects or cause execution to resume from a different evaluation.

Instead, the idea is that `breakpoint` is not responsible for causing the translation process
to make special accomodations for resumption of execution other than in cases
where the debugger was strictly used for observation only.

In `is_debugger_present`, the functionality ascribed to POSIX by the wording
("ptrace") is not present in POSIX. Update to reference the LSB and to use
the corresponding terminology ("tracing process").

The wording implies a preference to return `true` in case it is unknown
whether a debugger is present. Add a critical "only" to fix that.

Author: hubert-reinterpretcast

source/diagnostics.tex

@@ -2447,10 +2447,13 @@
 The semantics of this function are \impldef{semantics of \tcode{breakpoint}}.
 
 \begin{note}
-When invoked, the execution of the program temporarily halts and execution is
-handed to the debugger until such a time as: The program is terminated by the
-debugger, or the debugger resumes execution of the program as if the function
-was not invoked.
+It is intended that, when invoked with a debugger present, the execution of the
+program temporarily halts and execution is handed to the debugger until the
+program is either terminated by the debugger or the debugger resumes execution
+of the program as if the function was not invoked. In particular, there is no
+intent for a call to this function to accomodate resumption of the program in a
+different manner. If there is no debugger present, execution of the program can
+end abnormally.
 \end{note}
 
 \end{itemdescr}
@@ -2486,12 +2489,13 @@
 \impldef{default semantics of \tcode{is_debugger_present}}.
 
 \begin{note}
-When tracing the execution of a program with a debugger, an implementation
-returns \tcode{true}. An implementation performs an immediate query, as needed,
-to determine if the program is traced by a debugger. On Windows or equivalent
-systems, this can be achieved by calling the \tcode{::IsDebuggerPresent()} Win32
-function. On POSIX, this can be achieved by checking for a tracer parent process,
-with best effort determination that such a tracer parent process is a debugger.
+It is intended that, using an immediate (uncached) query to determine if the
+program is being traced by a debugger, an implementation returns \tcode{true}
+only when tracing the execution of the program with a debugger. On Windows or
+equivalent systems, this can be achieved by calling the
+\tcode{::IsDebuggerPresent()} Win32 function. For systems compatible with
+ISO/IEC 23360:2021, this can be achieved by checking for a tracing process, with
+a best-effort determination that such a tracing process is a debugger.
 \end{note}
 
 \pnum