Fixing logging used by sonic_platform_base classes to prevent log pollution

[gordon-nexthop]

Description

Convert the module-level loggers in sonic_platform_base from
sonic_py_common.logger.Logger to sonic_py_common.syslogger.SysLogger:
bmc_base.py, redfish_client.py, sed_mgmt_base.py and bmc_fw_update.py.

Logger is a thin wrapper around the C syslog API, and its constructor calls
syslog.openlog(), which sets one identifier for the whole process. These modules
build a Logger at import time, so simply importing them renames every subsequent syslog
message emitted anywhere in the importing process.

SysLogger instead attaches a SysLogHandler to a named logging.Logger, so the identifier
belongs to the logger instance rather than to the process. Importing a module can no longer
change how unrelated code in the same process is tagged, and each module still logs under its
own name. This is already the pattern used by sonic_platform_base/sonic_xcvr/cdb/.

Motivation and Context

fixes: #760

How Has This Been Tested?

On hardware. Nexthop 4010 (x86_64-nexthop_4010-r0, HwSKU NH-4010, SONiC master,
Python 3.13) — deliberately a non-BMC platform, since the bug reaches those too.

1. ZTP import chain. A probe that mirrors what ztp-engine.py does — construct
   Logger('sonic-ztp'), log, import sonic_platform.platform, log again — with
   syslog.openlog wrapped to record every identifier it is called with:

   	openlog() idents, in order	effective process ident
   before	['sonic-ztp', 'redfish_client', 'bmc_base']	bmc_base
   after	['sonic-ztp']	sonic-ztp

   and the resulting /var/log/syslog lines:

   # before
   NOTICE sonic-ztp:  probe before-import: ZTP service started.
   NOTICE bmc_base:   probe after-import: ZTP service still running.
   # after
   NOTICE sonic-ztp:  probe before-import: ZTP service started.
   NOTICE sonic-ztp:  probe after-import: ZTP service still running.
   

2. The real ztp service. systemctl start ztp (ZTP admin mode disabled, so it just bails)
   now logs under its own identifier, and no bmc_base-tagged line was emitted by anything on
   the switch after the swap:

   INFO sonic-ztp[768842]: ZTP is administratively disabled.
   

3. No regression to BMC logging. Importing the modules and logging through them directly
   still produces their own identifiers — now with the PID, since SysLogger formats as
   %(name)s[%(process)d] — and RedfishClient still constructs:

   NOTICE redfish_client[768154]: ...
   NOTICE bmc_base[768154]: ...
   NOTICE sed_mgmt_base[768154]: ...
   

4. Platform API smoke test. show platform summary, show platform psustatus and
   docker exec pmon supervisorctl status were all healthy with the patched modules in place
   (pcied, psud, sensormond, stormond, syseepromd, thermalctld, xcvrd all RUNNING).

Additional Information (Optional)

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[mssonicbld]

/azp run

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[gordon-nexthop]

@benle7 would you mind taking a peak at this one!

[mssonicbld]

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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