Fix dodal for triggerable command

[rtuck99]

Removes deprecated usage of SignalX in favour of TriggerableCommand

Requires

• PVA TriggerableCommand should support enums bluesky/ophyd-async#1292

Instructions to reviewer on how to test:

1. Do thing x
2. Confirm thing y happens

Checks for reviewer

• Would the PR title make sense to a scientist on a set of release notes
• If a new device has been added does it follow the standards
• If changing the API for a pre-existing device, ensure that any beamlines using this device have updated their Bluesky plans accordingly
• Have the connection tests for the relevant beamline(s) been run via dodal connect ${BEAMLINE}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.14%. Comparing base (7916b43) to head (ce03515).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2091   +/-   ##
=======================================
  Coverage   99.14%   99.14%           
=======================================
  Files         344      344           
  Lines       13388    13388           
=======================================
  Hits        13274    13274           
  Misses        114      114           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.