fix: directives name clashes with apollo federation for link

[meskill]

Summary:
Briefly describe the changes made in this PR.

Issue Reference(s):
Fixes #... (Replace "..." with the issue number)

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• I have added relevant unit & integration tests.
• I have updated the documentation accordingly.
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[tusharmath]

This is an interesting approach where we by default add federation specific items if the flag is set but then we are scattering this sub-graph specific logic everywhere in our codebase. My recommendation is to add a top-level definitions field in Config where we can add any additional definitions, like in this case - @link these additional definitions aren't consumed by Tailcall but are outputed as it is.

[meskill]

not exactly, the approach is not to output the Tailcall directives that conflicts with federation directives. To make the sdl output federation compatible we need to include apollo spec with federation's @link and by doing so we can't now leave tailcall's usage and definitions of @link