#6293 Use batch inject for content scripts

[sosnovsky]

This PR uses batch inject for content scripts injection, instead of multiple calls

close #6293

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Tests (delete all except exactly one):

• Does not need tests (refactor only, docs or internal changes)

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• addresses the issue it closes (if any)
• code is readable and understandable
• is accompanied with tests, or tests are not needed
• is free of vulnerabilities
• is documented clearly and usefully, or doesn't need documentation

[martgil]

Hi @sosnovsky - there's nothing to merge here now as it was already in the master branch (from an already merged #6296).

[sosnovsky]

Oh, you're right - I copied changes from this PR to test #6296, and since it was merged earlier - this one can be closed.