feat(tftemplate): add datasource generation to tftemplate

[Codelax]

in cmd/tftemplate
>> go run .
? Choose targets
- [x] resource
- [ ] datasource
? API name (function, instance, container) block
? Resource name (FunctionNamespace, InstanceServer) BlockVolume
? Choose locality
> zone
  region
? Generate helpers ? Will override scaleway/helpers_{api}.go (y/N)
? Generate waiters ? Will be added to scaleway/helpers_{api}.go (Y/n)

[codecov-commenter]

Codecov Report

Merging #2017 (8e7dfbc) into master (68bd185) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2017   +/-   ##
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  Coverage   73.94%   73.94%           
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  Files         182      182           
  Lines       28648    28648           
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  Hits        21184    21184           
  Misses       5653     5653           
  Partials     1811     1811