Optimizes and caches `getTokensFromTemplate`

Ensures view node parent overrides

Refs: #2680

- Adds ai.experimental.provider setting to switch between OpenAI & Anthropic

- Moves AI settings into a new AI section
 - Renames new setting into a `gitlens.ai` namespace and changes it to be an enum for easier selection
 - Updates max characters to be dependent on selected model

Refs: #2680

Refs #2677

- adds color to push and pull actions
- shows fetch action always

- Moves _Copy Remote \* URL_ from _Copy As_ to _Share_
 - Moves _Copy SHA_,  _Copy Message_,  _Copy Relative Path_ from _Copy As_ to root