Use cached property in commands validation

Description

This just moves to code to use a nicer pattern for cached properties. This required a slight change in when the exclude intervals are fetched from Google sheets.

The PR also makes one small out-of-scope change to remove the unused update_tlm() base method. That originally served a purpose but is no longer used.

Interface impacts

Testing

Used local ska3-performance installation.

Unit tests

[x] Mac (importantly the newly-available validation regression tests)


(ska3-perf) ➜  kadi git:(use-cached-property) git rev-parse HEAD             
87bf8716ac03e51bef60a2f53f21d609df3e67f9
(ska3-perf) ➜  kadi git:(use-cached-property) pytest kadi
==================================================== test session starts ====================================================
platform darwin -- Python 3.10.8, pytest-7.2.1, pluggy-1.0.0
rootdir: /Users/aldcroft/git, configfile: pytest.ini
plugins: timeout-2.1.0, anyio-3.6.2
collected 218 items

kadi/commands/tests/test_commands.py ........................................................................... [ 34%] kadi/commands/tests/test_states.py ......................x.............................................x............. [ 72%] .......... [ 76%] kadi/commands/tests/test_validate.py ................... [ 85%] kadi/tests/test_events.py .......... [ 89%] kadi/tests/test_occweb.py ...................... [100%]

======================================== 216 passed, 2 xfailed in 135.94s (0:02:15) =========================================



Independent check of unit tests by Jean
- [x] Linux

### Functional tests
<!-- Describe and document results of any functional tests, otherwise leave the text below -->
No functional testing.

sot / kadi