Make enabled_feature? return true when all flags are enabled

[vinistock]

Motivation

When fixing the mistake on the feature flags object composition, I also noticed that the global state wouldn't return true if the user had their configuration set as

{
  "rubyLsp.featureFlags": {
    "all": true
  }
}

which is not correct. If they enabled all flags, then checking with enabled_feature? should return true.

Implementation

Started returning true if all is enabled.

Automated Tests

Added a test.

[vinistock]

• Make enabled_feature? return true when all flags are enabled #2900 👈 (View in Graphite)
• Fix enabled feature flags object composition #2899
• main

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