utils: share one ls-permission-field parser across NetRocks and adb, and fix its set-id handling - #3533

Depends on #3531 — this branch is stacked on it, so the first four commits shown here belong to that PR. Only the last commit, utils: share one ls-permission-field parser…, is new. Happy to rebase once #3531 is resolved, or to drop the adb/ hunk and land the utils/ + NetRocks/ part on its own if you prefer.

Recovering a mode_t from the textual permission field of an ls -l line was implemented three times — NetRocks' ShellParseUtils (SHELL and SCP), NetRocks' vendored FTP LIST parser, and the adb plugin — and all three mishandled the set-id and sticky spellings.

ShellParseUtils tested the wrong character:

if (c[2] == 'x' || c[1] == 's' || c[1] == 't') out |= 1;

c[1] is the write position, which is never s or t, so the execute bit was dropped for every set-id or sticky entry. And S_ISUID / S_ISGID / S_ISVTX were never extracted at all. far2l renders exactly those out of dwUnixMode (panelmix.cpp), so on a remote listing /system/bin/run-as showed up as -rwxr-xr-x and /tmp as drwxrwxrwx.

This moves one implementation into utils/include/UnixModeStr.h and deletes all three copies. The header is enough on its own: the top-level CMakeLists.txt already does include_directories(utils/include), so every target sees it without build changes.

FTPParseLIST was looser still — any character but - sets the bit — so -rwSr--r-- came out executable, and NetWare's d [RWCEAFMS] … form yielded 0777 from the bracketed flags instead of no permission bits:

Net effect: 78 insertions against 124 deletions across 6 files.

Correctness

Table-tested against the previous NetRocks implementation over 17 field shapes — plain / dir / symlink / char / block / fifo / socket, s and S, t and T, truncated fields, and the d????????? form a shell emits for entries it may not stat. The new parser matches expectations on all 17; the old one was wrong on 6, every one of them set-id or sticky:

Behaviour changes worth naming

• far2l renders these bits from dwUnixMode (mix/panelmix.cpp:487-493), so SHELL, SCP and FTP listings now show them, and FILE_ATTRIBUTE_EXECUTABLE is now set for entries like -rwsr-xr-x. WinPort derives its attribute flags from S_IFMT plus the r/w/x bits only (WinPort/src/APIFiles.cpp:24-49), so nothing else in that mapping moves. SFTP is unaffected — it takes real permissions from the sftp attributes.
• Op/OpXfer.cpp propagates the source mode on copy (:469 SetMode, :513 FilePut, :626 DirectoryCreate). Those bits could not previously be present for a SHELL/SCP/FTP source, so copying a setuid binary from such a host now reproduces the setuid bit at the destination where before it silently did not. That matches what a local-to-local copy already does via real stat(2), but it is a privilege-bit change rather than a cosmetic one, so please weigh it.
• OpChangeMode now pre-checks the suid/sgid/sticky boxes for these items.

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