gh-154060: Fix the Profile Stats offsets in the profiling binary format docs and a missing flag

[maurycy]

The file layout diagram in:

https://github.com/python/cpython/blob/a64b7ecba4db5480504a1a83ae6e80c81472fe16/InternalDocs/profiling_binary_format.md#file-layout

says that the Profile Stats section is 32 bytes and starts at file_size - 64, while it's 56 bytes and starts at file_size - 88 (56 + 32 = 88).

cpython/Modules/_remote_debugging/binary_io.h

Lines 122 to 123 in a64b7ec

	static_assert(PROFILE_STATS_SIZE == 56,
	"PROFILE_STATS_SIZE must remain 56");

cpython/Modules/_remote_debugging/binary_io.h

Lines 91 to 92 in a64b7ec

	static_assert(FILE_FOOTER_SIZE == 32,
	"FILE_FOOTER_SIZE must remain 32");

The test:

cpython/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py

Lines 1655 to 1660 in a64b7ec

	with open(bin_path, "rb") as file:
	data = file.read()
	stats = data[-88:-32]
	footer = bytearray(data[-32:])
	old_stats = stats[:16] + b"TACHSTAT" + struct.pack("=II", 1, 32)
	old_data = bytearray(data[:-88] + old_stats + footer)

Even the doc itself says 56 bytes later:

New files can store measured duration, sampling rate, error rate, and missed sample percentage in an optional 56-byte extension immediately before the footer.

Both the diagram and the section is since 7f0ccd6.

While we're at it, adding THREAD_STATUS_MAIN_THREAD flag missed from the docs.

Hardly newsworthy, hardly testable but I think would be nice to backport to 3.15.

https://github.com/python/cpython/pull/154105/changes#diff-43a2fe1b7de3546d9e026fcf3664cdc0c35608385926a09e8038a84598acba30 addresses another issue in the document (Total sample count is now uint64.)

• Issue: Tachyon flamegraph: Replaying binary file doesn’t show time/rate in sidebar #154060

[maurycy]

cc @pablogsal 🖤

[maurycy]

Suggested change

	| 5 | THREAD_STATUS_MAIN_THREAD | Thread is the process's main thread |
	| 5 | THREAD_STATUS_MAIN_THREAD | Thread is the interpreter's main thread |

Very formally speaking I think that's the case... I don't know if should expose this, though. Leaving as a suggestion, so the reviewer can just click or resolve.