contrib: Fixup verify-binaries OS platform parsing

Parse platform strings with "-" or '.' correctly such as "linux-gnu" or
"x86_64-linux-gnu.tar.gz" to download the matching files or file. String
partition() is used to tolerate more dashes. Update `VERSION_EXAMPLE`
with a new string parsed correctly now. Fix "-aarch64" interpreted as a
release candidate due to sub-string "rc", causing all downloads to fail.
Now "rc" must immediately follow first "-" to indicate an [-rc] string.
Local variables `version_rc`, `version_os` renamed to `rc`, `platform`.
If "-rcN" is specified, `platform` is reassigned to remove the '-rcN'.

Changes are useful to only download one bitcoin core binary on slow
connections. Making `verify.py pub` more intuitive, robust, and
versatile. Closes #30145

When user types a platform string not found in any filename lets help
and say the platform closest to what they typed in a `f"No files
matched the platform specified. Did you mean: {closest_match}"` log.
Improves UX when unaware how we name our files.
Uses the difflib Python built-in which was already imported elsewhere.

Update test.py to test single file verification
verify-binaries/verify.py can accept an entire filename filter for its
"-platform" parameter now so let us test that it succeeds and downloads
and verifies only one file. `verify.py pub 22.0-x86_64-linux-gnu.tar.gz`
should get and verify only the requested binary. It is placed before the
existing <version> wide verification as it is a faster test and possibly
easier to break.

Update doc with examples now possible after bugfix
Add example to show release candidates now work with "-platform" strings
containing "-" and string provided can be from the middle of filename:
`./contrib/verify-binaries/verify.py --json pub 23.0-rc5-linux-gnu`
Change example 5 to not match example 3.
New examples to show platform can now be provided specifically enough to
download only a single binary down to its file extension:
`./contrib/verify-binaries/verify.py pub 25.2-x86_64-linux`
`./contrib/verify-binaries/verify.py pub 24.1-rc1-darwin`
`./contrib/verify-binaries/verify.py pub 27.0-win64-setup.exe`
This is the most common use if not verifying all files so users see it
as the first example for "only download the binaries for a certain
architecture and/or platform". Downloading one file is intuitively what
most will think this meant and this change delivers on that expectation.

Co-authored-by: stickies-v

contrib/verify-binaries/test.py

@@ -12,6 +12,21 @@ def main():
     expect_code(run_verify("", "pub", '0.32.awefa.12f9h'), 11, "Malformed version should fail")
     expect_code(run_verify('--min-good-sigs 20', "pub", "22.0"), 9, "--min-good-sigs 20 should fail")
 
+    print("- testing verification (22.0-x86_64-linux-gnu.tar.gz)", flush=True)
+    _220_x86_64_linux_gnu = run_verify("--json", "pub", "22.0-x86_64-linux-gnu.tar.gz")
+    try:
+        result = json.loads(_220_x86_64_linux_gnu.stdout.decode())
+    except Exception:
+        print("failed on 22.0-x86_64-linux-gnu.tar.gz --json:")
+        print_process_failure(_220_x86_64_linux_gnu)
+        raise
+
+    expect_code(_220_x86_64_linux_gnu, 0, "22.0-x86_64-linux-gnu.tar.gz should succeed")
+    v = result['verified_binaries']
+    assert result['good_trusted_sigs']
+    assert len(v) == 1
+    assert v['bitcoin-22.0-x86_64-linux-gnu.tar.gz'] == '59ebd25dd82a51638b7a6bb914586201e67db67b919b2a1ff08925a7936d1b16'
+
     print("- testing verification (22.0)", flush=True)
     _220 = run_verify("--json", "pub", "22.0")
     try: