Support split subsetting

[Konboi]

To support split subset for v2 (a.k.a smart-tests)

Usage

 $smart-tests subset file --session @session.txt --subset-id 286 --bin 1/2 --target 20%
tests/commands/test_api_error.py
tests/commands/test_verify.py
tests/test_runners/test_jasmine.py
tests/args4p/converters/__init__.py
tests/commands/record/test_case_event.py
tests/data/pytest/tests/funcs3_test.py
tests/utils/test_gzipgen.py
tests/test_runners/test_adb.py
Smart Tests created subset 287 for build  (test session 513) in workspace konboi/pts-v2

|           |   Candidates |   Estimated duration (%) |   Estimated duration (min) |
|-----------|--------------|--------------------------|----------------------------|
| Subset    |            8 |                    19.05 |                       0.00 |
| Remainder |           34 |                    80.95 |                       0.00 |
|           |              |                          |                            |
| Total     |           42 |                   100.00 |                       0.00 |

Run `smart-tests inspect subset --subset-id 287` to view full subset details
$ smart-tests subset file --session @session.txt --subset-id 287 --bin 1/2 --target 5%
tests/commands/test_api_error.py
tests/commands/test_verify.py
Smart Tests created subset 288 for build  (test session 513) in workspace konboi/pts-v2

|           |   Candidates |   Estimated duration (%) |   Estimated duration (min) |
|-----------|--------------|--------------------------|----------------------------|
| Subset    |            2 |                     4.76 |                       0.00 |
| Remainder |           40 |                    95.24 |                       0.00 |
|           |              |                          |                            |
| Total     |           42 |                   100.00 |                       0.00 |