vnet: add SFF8472 and SFF8636 diagnostics

vnet: add SFF8472 and SFF8636 diagnostics

Using device-class.eeprom_read_function, extract the type of
EEPROM, and create a parser for SFF8472 (SFP+/SFP/SFP28) and
SFF8636 (QSFP+/QSFP28/QSFP-DD) to show module diagnostics.

When available, read EEPROM page A2h and report on DDM values:
show int transceiver <itf> eeprom
show int transceiver <itf> module [verbose]
show int transceiver <itf> diag [verbose]

Type: improvement
Change-Id: Iae41b9753f31bc1a8d32b2c42d396cd743864147
Signed-off-by: [email protected]