feat: feature flag

[jif-oai]

Add proper feature flag instead of having custom flags for everything. This is just for experimental/wip part of the code
It can be used through CLI:

codex --enable unified_exec --disable view_image_tool

Or in the config.toml

# Global toggles applied to every profile unless overridden.
[features]
apply_patch_freeform = true
view_image_tool = false

Follow-up:
In a following PR, the goal is to have a default have bundles of features that we can associate to a model

[chatgpt-codex-connector]

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[jif-oai]

@codex review

[chatgpt-codex-connector]

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[byteprobe]

yes please! 🙌

[dylan-hurd-oai]

Couple of comments to resolve - but overall I like this interface!

[dylan-hurd-oai]

1 final comment, LGTM otherwise!