add a new run command along with a new flag

[tejal29]

Relates to snapshotting is slow issue.

In this Pr, i am experimenting a new run command implemetation.
Next steps would be to run kaniko with this flag on GCB for different memory config and files. #1299

[tejal29]

Performance improvement

Number of Files | Total Build Time Full Snapshot - current | Total Build Time - Snapshot None | %decrease
-- | -- | -- | --
10000 | 13.834973 | 8.111625 | 41.37%
50000 | 47.926338 | 32.676982 | 31.82%
100000 | 96.440554 | 56.665994 | 41.24%
200000 | 187.346273 | 123.323148 | 34.17%
300000 | 341.233622 | 175.900867 | 48.45%
500000 | 1404.410121 | 303.784665 | 78.37%
700000 | 1772.379601 | 428.679737 | 75.81%