azp: go-to-definition to jump to the template file

[ChristopherHX]

template: ./path/t.yml # <--- shift click should open the file

[ChristopherHX]

Remote templates need caching of template hierarchies / approximation of possible ones

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Static template references can now be followed:

• on web even for unititled docs the editor opens even non existent files
• doing this on a missing on disk saved template results in file not found error