Separate tab behavior from inline completion

[raphaelluethy]

This PR allows for the complete separation of the Tab key and the inline completions provided by Copilot or Supermaven.

Contributors: Thanks again to @ConradIrwin for the co-session!

Release Notes:

• Added editor::AcceptInlineCompletion action (bound to Tab by default). To prevent accepting inline completions with tab, add {"context": "Editor && inline_completions", "bindings": {"tab": "editor::Tab"}}. (Fixes #6788)

[zed-industries-bot]

	Warnings
:warning:	This PR is missing release notes. Please add a "Release Notes" section that describes the change: Release Notes: - (Added|Fixed|Improved) ... ([#<public_issue_number_if_exists>](https://github.com/zed-industries/zed/issues/<public_issue_number_if_exists>)). If your change is not user-facing, you can use "N/A" for the entry: Release Notes: - N/A

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[raphaelluethy]

Can you do those changed on the PR? Since I have no idea how to do that 😅