Add fastcs eiger to i15-1

[jacob720]

Adds the fastcs eiger to i15-1. Needs the new ophyd async version so based on top of #1979

Instructions to reviewer on how to test:

1. Do dodal connect i15-1
2. Confirm fastcs_eiger connects

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.
⚠️ Please upload report for BASE (update_dodal_ophyd_async_v0.17a1@26e4fe1). Learn more about missing BASE report.

Additional details and impacted files

@@                         Coverage Diff                         @@
##             update_dodal_ophyd_async_v0.17a1    #2058   +/-   ##
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  Files                                       ?      325           
  Lines                                       ?    12673           
  Branches                                    ?        0           
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  Hits                                        ?    12553           
  Misses                                      ?      120           
  Partials                                    ?        0           

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