fix: check command before running analyze

[naiyoma]

fixes: #44

We check the command before running analyze

Previously: A bad command (e.g. an invalid --run_test filter, which makes Boost exit 200) failed for every mutant. Each failure was recorded as killed, so the run reported a
incorrect 100% mutation score.

STDERR:
Test setup error: no test cases matching filter or all test cases were disabled

  KILLED ✅
Executing command: git restore src/net_processing.cpp

Now: The run aborts immediately with a clear error, no mutants are analyzed (they stay pending), and the process exits non-zero.

bcm analyze --sqlite --run-id=1 -c "build/bin/test_bitcoin --run_test=nope_not_real"
Analyzing mutants for project: Bitcoin Core
* 13 MUTANTS in run_id=1 *
Baseline check: running the test command on unmutated code...
Executing command: build/bin/test_bitcoin --run_test=nope_not_real
Command exit code: 200
STDERR:
Test setup error: no test cases matching filter or all test cases were disabled

Error: InvalidInput("Test command failed before any mutant was applied. Fix the command and re-run. Command: build/bin/test_bitcoin --run_test=nope_not_real")

[brunoerg]

Sorry for the delay, not sure why I did not receive the notification about it.

[brunoerg]

ACK 203b15b