sys/log: Add optional support for sector bookmarks to optimize reading logs

[vrahane]

• This adds sector bookmarks for reading optimization, earlier only absolute bookmarks were supported
• Retain older absolute bookmarks behavior. Added a syscfg for specifying number of absolute bookmarks.
• Added a syscfg to optionally enable sector bookmarks.
• CLI: Add '-i' option in log_shell for specifying index where log read should start
• CLI: Add '-b' option in log_shell for reading bookmarks

For mixed bookmarks:

• Sector bookmarks are from 0 -> sector_cnt of the flash area in the array.
• Non-sector/Absolute bookmarks are from sector_cnt -> LOG_FCB_NUM_ABS_BMARKS (2 by default)

Several tests were performed:

• Reboot test, bookmarks should get reset
• New log entries populate the bookmarks, specially for sector boundaries
• Test absolute bookmarks behavior, both with mixed bookmarks (sector + absolute) as well as just absolute bookmarks with sector bookmarks disabled

[kasjer]

• Code will not build for FCB2
• It's not clear how to choose size for bookmarks array
• If suggested size is around number of sector of the FCB flash area, RAM usage can be an issue. For 384 sectors' FCB RAM usage is over 12KB
• There are places that use code and RAM space even if no bookmarks/sector-bookmarks are enabled

[vrahane]

Note: The style check incorrectly flags the unit test functions. It does not understand that its a function, it thinks its a code block.

[sjanc]

Note: The style check incorrectly flags the unit test functions. It does not understand that its a function, it thinks its a code block.

yes, there are couple of uncrustify config tuning needed that I haven't figure out yet (especially those related to macros as in here). So we hit false-positive with this from time to time...