Tools: bugfix: singletes.py was not reporting test case build failure

[PrzemekWirkus]

Description

1. singletest.py was not reporting in summary table or other reports test case build failure. Thi issue was observed in team's internal CI server.
2. Added new error code to sibgletst.py called BUILD_FAILURE - used when test case build fails.
3. Added new summary: Build successful, skipped and failed - the same summary as in build.py.

Example of test case build failure:

.
.
Building project DETECT (K64F, ARM)
Compile: main.cpp
[Error] main.cpp@4:  #35: #error directive: Error added for test
[23:19:24] Error: There were errors while building project DTCT_1
.
.

Example of fixed behavior where singletest.py is fetching information about failed test case build and passing to results tables (also JUnit and HTML reports).
In below example test DICT_1 is failing to build and summary is enriched with BUILD_FAILURE

$ singletest.py --auto -j 8 -n DTCT_1,RTOS_1 --report-html hr.html
MBEDLS: Detecting connected mbed-enabled devices...
MBEDLS: Detected K64F, port: COM61, mounted: I:
Building library CMSIS (K64F, ARM)
Building library MBED (K64F, ARM)
Building library RTOS (K64F, ARM)
Building library RTX (K64F, ARM)
Building project DETECT (K64F, ARM)
Compile: main.cpp
[Error] main.cpp@4:  #35: #error directive: Error added for test
[23:19:24] Error: There were errors while building project DTCT_1
Building project BASIC (K64F, ARM)
TargetTest::K64F::ARM::RTOS_1::Basic thread [OK] in 11.33 of 15 sec
Test summary:
+--------------+--------+-----------+---------+------------------------+--------------------+---------------+-------+
| Result       | Target | Toolchain | Test ID | Test Description       | Elapsed Time (sec) | Timeout (sec) | Loops |
+--------------+--------+-----------+---------+------------------------+--------------------+---------------+-------+
| BUILD_FAILED | K64F   | ARM       | DTCT_1  | Toolchain build failed |         0          |       0       |   -   |
| OK           | K64F   | ARM       | RTOS_1  | Basic thread           |       11.33        |       15      |  1/1  |
+--------------+--------+-----------+---------+------------------------+--------------------+---------------+-------+
Result: 1 BUILD_FAILED / 1 OK

Completed in 20.83 sec

Build successes:
  * ARM::K64F

Build failures:
  * ARM::K64F::DTCT_1

[PrzemekWirkus]

This will fix:

[DEBUG] Command: C:/mbed_tools/ARMCompiler_5.03_117_Windows\bin\fromelf --bin -o C:\Jenkins\jobs\mbed_2.0_build_release_test_publish\workspace\build\test\NRF51822\ARM\DTCT_1\detect.hex C:\Jenkins\jobs\mbed_2.0_build_release_test_publish\workspace\build\test\NRF51822\ARM\DTCT_1\detect.elf
[DEBUG] Return: 0
[DEBUG] Merge SoftDevice file s110_nrf51822_8.0.0_softdevice.hex
Traceback (most recent call last):
  File "./workspace_tools/singletest.py", line 237, in <module>
    singletest_in_cli_mode(single_test)
  File "C:\Jenkins\jobs\mbed_2.0_build_release_test_publish\workspace\workspace_tools\test_api.py", line 1419, in singletest_in_cli_mode
    test_summary, shuffle_seed, test_summary_ext, test_suite_properties_ext, build_report = single_test.execute()
  File "C:\Jenkins\jobs\mbed_2.0_build_release_test_publish\workspace\workspace_tools\test_api.py", line 543, in execute
    self.execute_thread_slice(q, target, toolchains, clean, test_ids, cur_build_report)
  File "C:\Jenkins\jobs\mbed_2.0_build_release_test_publish\workspace\workspace_tools\test_api.py", line 482, in execute_thread_slice
    single_test_result, detailed_test_results = self.handle(test_spec, target, toolchain, test_loops=test_loops)
TypeError: 'NoneType' object is not iterable

when None object is passed as port or mount point from e.g. mbed-ls tools