refactor: add ListID to datasourceutil package

[jooola]

Reuse a function to compute the data source list IDs.

[codecov]

Codecov Report

Attention: Patch coverage is 27.77778% with 13 lines in your changes missing coverage. Please review.

Project coverage is 34.28%. Comparing base (ed5156b) to head (fbe8c70).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/certificate/data_source.go	0.00%	1 Missing ⚠️
internal/datacenter/data_source.go	0.00%	1 Missing ⚠️
internal/firewall/data_source.go	0.00%	1 Missing ⚠️
internal/floatingip/data_source.go	0.00%	1 Missing ⚠️
internal/image/data_source.go	0.00%	1 Missing ⚠️
internal/loadbalancer/data_source.go	0.00%	1 Missing ⚠️
internal/location/data_source.go	0.00%	1 Missing ⚠️
internal/network/data_source.go	0.00%	1 Missing ⚠️
internal/placementgroup/data_source.go	0.00%	1 Missing ⚠️
internal/primaryip/data_source.go	0.00%	1 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #989      +/-   ##
==========================================
+ Coverage   34.24%   34.28%   +0.04%     
==========================================
  Files          64       65       +1     
  Lines        7972     7977       +5     
==========================================
+ Hits         2730     2735       +5     
  Misses       5201     5201              
  Partials       41       41              

Flag	Coverage Δ
unit	34.28% <27.77%> (+0.04%)	⬆️

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