Improve detection of runner health

[yhaliaw]

Uses whether the runner script process is running as the health check for the runner.

[gregory-schiano]

LGTM

[github-actions]

Test coverage for dc468ad

Name                                    Stmts   Miss Branch BrPart  Cover   Missing
-----------------------------------------------------------------------------------
src/charm.py                              371     86     86     21    74%   126-128, 182-190, 202-206, 275->279, 300-305, 315, 324-325, 334-345, 362-364, 372-375, 381, 392, 403->420, 408-413, 430-431, 435-436, 441-444, 457-458, 460-461, 495-503, 514-515, 533-535, 538->exit, 542-544, 567-572, 590-591, 593-594, 596-597, 629->631, 690-691, 704, 717
src/errors.py                              22      0      0      0   100%
src/event_timer.py                         42      8      4      0    74%   96-99, 119-122
src/firewall.py                            43     25     10      0    38%   38-42, 64-67, 75-149
src/github_type.py                         36      0      0      0   100%
src/lxd_type.py                            38      0      2      0   100%
src/repo_policy_compliance_service.py       5      5      0      0     0%   4-14
src/runner.py                             249     29     74     21    84%   40->44, 188-195, 201-207, 266-271, 276, 296, 329->332, 335-337, 344, 358, 368, 372, 374, 389, 433-438, 448, 532, 567, 593, 598-610, 624, 642
src/runner_manager.py                     219     25     88      9    88%   204-206, 219-220, 232-234, 240-245, 249-250, 260-261, 277, 332, 357-361, 380, 398, 541, 561
src/runner_type.py                         52      0     12      0   100%
src/utilities.py                           66      5     18      7    86%   74->76, 78->84, 89-91, 119, 164, 217
-----------------------------------------------------------------------------------
TOTAL                                    1143    183    294     58    81%

Static code analysis report

Run started:2023-07-17 08:00:21.608562

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 2562
  Total lines skipped (#nosec): 0
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 9

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):

[yanksyoon]

LGTM!