Add Earth Time (UTC) to msl/m20/nyst/mer-date

[kmgill]

Provides system clock validation.

[kmgill]

*-date command output updated as:

$ mru msl-date
Earth Time (UTC):       Sun,  1 Oct 2023 17:12:27 UTC
Earth DOY (UTC):        2023-274T17:12:27.000
Mars Sol Date:          53233.75243578409
Coordinated Mars Time:  18:03:30.452
Mission Sol:            3965
Mission Time:           03:13:16.460 LMST
Local True Solar Time:  03:38:53.547 LTST
Solar Longitude:        126.82268729651614

$ mru m20-date
Earth Time (UTC):       Sun,  1 Oct 2023 17:13:17 UTC
Earth DOY (UTC):        2023-274T17:13:17.000
Mars Sol Date:          53233.75300146653
Coordinated Mars Time:  18:04:19.327
Mission Sol:            929
Mission Time:           23:14:02.527 LMST
Local True Solar Time:  23:39:39.619 LTST
Solar Longitude:        126.82296429510076

$ mru nsyt-date
Earth Time (UTC):       Sun,  1 Oct 2023 17:13:34 UTC
Earth DOY (UTC):        2023-274T17:13:34.000
Mars Sol Date:          53233.7531948393
Coordinated Mars Time:  18:04:36.034
Mission Sol:            1723
Mission Time:           03:07:05.650 LMST
Local True Solar Time:  03:32:42.744 LTST
Solar Longitude:        126.82305898428704

$ mru mer-date
MER-A / Spirit:
Earth Time (UTC):       Sun,  1 Oct 2023 17:13:50 UTC
Earth DOY (UTC):        2023-274T17:13:50.000
Mars Sol Date:          53233.753370858954
Coordinated Mars Time:  18:04:51.242
Mission Sol:            7017
Mission Time:           18:04:51.242 LMST
Local True Solar Time:  18:30:28.338 LTST
Solar Longitude:        126.82314517616575
-----------------------------------------------
MER-B / Opportunity:
Earth Time (UTC):       Sun,  1 Oct 2023 17:13:50 UTC
Earth DOY (UTC):        2023-274T17:13:50.000
Mars Sol Date:          53233.75337087844
Coordinated Mars Time:  18:04:51.244
Mission Sol:            6998
Mission Time:           17:03:45.205 LMST
Local True Solar Time:  17:29:22.301 LTST
Solar Longitude:        126.82314518570902