[eeprom] Use swsscommon instead of redis-py in eeprom_tlvinfo.

[jianyuewu]

Why I did it

The TlvInfo EEPROM decoder imported redis-py at module top level.
redis-py is heavy (~20MB RSS on import), and this cost is paid by every process that imports the decoder, even those that only decode the EEPROM buffer and never touch the DB.

Work item tracking

• Microsoft ADO (number only): N/A

How I did it

Replaced redis-py with swsscommon's SonicV2Connector, which is already loaded in these daemons and is the standard SONiC DB accessor:

• Dropped the top-level import redis and the STATE_DB_INDEX constant, and dropped redis from setup.py install_requires (no longer imported anywhere under sonic_platform_base/).
• Renamed the redis_client property to state_db, returning a lazily connected SonicV2Connector bound to STATE_DB. It connects with retry_on=False so an unreachable STATE_DB fails fast, matching the old redis client (which raised ConnectionError rather than hanging).
• _redis_hget reads via SonicV2Connector.get, which returns a decoded str, so the previous .decode() is dropped; rstrip('\0') is kept.
• EepromRedisVisitor writes via a new _hmset helper that coerces field values to str (SonicV2Connector.hmset requires str values, whereas redis-py stringified them implicitly), so int fields such as Version and Total Length are stored exactly as before.
• Also removed an unused from . import sfp_base in chassis_base.py (referenced nowhere except a docstring).

The EEPROM_INFO key space and field names are unchanged, so all consumers (show platform syseeprom, gNMI, etc.) are unaffected.

How to verify it

• On device manual test: show platform syseeprom, decode-syseeprom, and decode-syseeprom -d return identical output before and after; EEPROM_INFO|* contents in STATE_DB are byte-for-byte identical.

daemon	before (MB)	after (MB)	diff
syseepromd	24.5	15.3	-9.2 (-37%)

• Platform regression test: all passed.

Which release branch to backport (provide reason below if selected)

Tested branch

• master_RC

Test result

master_RC: PASSED (unit tests + on-device syseeprom output / STATE_DB comparison)

Description for the changelog

[eeprom] Use swsscommon instead of redis-py in eeprom_tlvinfo to drop the redis-py import from every process that decodes the syseeprom.

[mssonicbld]

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