feat: make session snapshot more full proof#786

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soumyamahunt wants to merge 5 commits into0x7c13:masterfrom soumyamahunt:robust-sessionsnapshot

+343-69

Commits on Feb 19, 2021

Use alternate write method for session snapshot.
soumyamahunt
committed

Commits on Feb 21, 2021

Implemented recovering tabs from orphaned backup files and fewer IO operations during session snapshot load.
soumyamahunt
committed
Delete temp files after sessions loaded.
soumyamahunt
committed

Commits on Feb 22, 2021

Implemeted recovering sessions from .~TMP files.
soumyamahunt
committed

Commits on Mar 29, 2021

Resolve conflicts.
soumyamahunt
committed