HLD for diagnostic monitoring of CMIS based transceivers (#1828)

* HLD for diagnostic monitoring of CMIS based transceivers

Signed-off-by: Mihir Patel <[email protected]>

* Addressed review comments

* Addressed review comments

* Added section for transceiver OIR handling for updating redis-db

* Modified CLI output for the diagnostic monitoring related CLIs

* Removed change_count, last_set_time and last_clear_time from field names of all the relevant tables

* Added dom_last_update_time and dom_update_interval to TRANSCEIVER_STATUS table

* Enhanced section 4.2.6

* Renumbered flag related sections to be part of section 4.2.3

* Removed _flag from fields of FLAG related tables

* Changed TRANSCEIVER_VDM_CURRENT_SAMPLE to TRANSCEIVER_VDM_REAL_VALUE and enhanced the output of various CLIs using lane number

* Modified TRANSCEIVER_VDM_THRESHOLD to TRANSCEIVER_VDM_XXX_THRESHOLD

* Updated info on dynamic updation of diagnostic monitoring, added description of using EWMA to update diagnostics_update_interval and added info using first subport only for breakout port config

* Updated info on behavior of flags due to latched behavior

* Addressed PR comments and added section for Link Change Event detection

* Added a section for exceptions and changed the link change detection logic

* Added usage of MAX_VDM_FREEZE_UNFREEZE_TIME_MSECS

* Added Reason for not relying on PORT_TABLE notifications for link change detection

* Updated time change details for capturing flag change event in xcvrd

* Moved vdm_support and vdm_fine_interval_length fields to TRANSCEIVER_INFO table

---------

Signed-off-by: Mihir Patel <[email protected]>