Refactor EVChargerType enum variants (#21)

The enum with the oder variants was compiled into the following rust
enum (by prost):
```rust
pub enum EvChargerType {
    /// Default type.
    EvchargerTypeUnspecified = 0,
    /// The EV charging station supports AC charging only.
    EvchargerTypeAc = 1,
    /// The EV charging station supports DC charging only.
    EvchargerTypeDc = 2,
    /// The EV charging station supports both AC and DC.
    EvchargerTypeHybrid = 3,
}
```
Here the enum variants were unnecessarily prefixed with `EvchargerType`.
This lead to accessing the enum variants in a very verbose manner, e.g.,
`EvChargerType::EvchargerTypeHybrid`.

The changed version of the enum in this commit results in the following
rust enum:
```rust
pub enum EvChargerType {
    /// Default type.
    Unspecified = 0,
    /// The EV charging station supports AC charging only.
    Ac = 1,
    /// The EV charging station supports DC charging only.
    Dc = 2,
    /// The EV charging station supports both AC and DC.
    Hybrid = 3,
}
```
Here the unnecessary prefix `EvchargerType` is absent. This reduces the
verbosity while accessing the enum variants, making the resulting rust
code more readable, e.g., as `EvChargerType::Hybrid`.

Author: tiyash-basu-frequenz

RELEASE_NOTES.md

@@ -15,6 +15,46 @@
   Synchronizing submodule url for 'submodules/api-common-protos'
   ```
 
+* [`EVChargerType` enum refactored](https://github.com/frequenz-floss/frequenz-api-common/pull/21)
+
+  The enum with the oder variants was compiled into the following rust enum
+  (by prost):
+  ```rust
+  pub enum EvChargerType {
+      /// Default type.
+      EvchargerTypeUnspecified = 0,
+      /// The EV charging station supports AC charging only.
+      EvchargerTypeAc = 1,
+      /// The EV charging station supports DC charging only.
+      EvchargerTypeDc = 2,
+      /// The EV charging station supports both AC and DC.
+      EvchargerTypeHybrid = 3,
+  }
+  ```
+  Here the enum variants were unnecessarily prefixed with `EvchargerType`.
+  This lead to accessing the enum variants in a very verbose manner, e.g.,
+  `EvChargerType::EvchargerTypeHybrid`.
+
+  The changed version of the enum in this commit results in the following
+  rust enum:
+  ```rust
+  pub enum EvChargerType {
+      /// Default type.
+      Unspecified = 0,
+      /// The EV charging station supports AC charging only.
+      Ac = 1,
+      /// The EV charging station supports DC charging only.
+      Dc = 2,
+      /// The EV charging station supports both AC and DC.
+      Hybrid = 3,
+  }
+  ```
+  Here the unnecessary prefix `EvchargerType` is absent. This reduces the
+  verbosity while accessing the enum variants, making the resulting rust code
+  more readable, e.g., as `EvChargerType::Hybrid`.
+
+  This change also leads to renaming the enum from `EVChargerType` to
+  `EvChargerType`, to satisfy protolint requirements.
 ## New Features
 
 <!-- Here goes the main new features and examples or instructions on how to use them -->

proto/frequenz/api/common/components.proto

@@ -75,18 +75,18 @@ enum InverterType {
 }
 
 // Enumerated EV charger types.
-enum EVChargerType {
+enum EvChargerType {
   // Default type.
-  EVCHARGER_TYPE_UNSPECIFIED = 0;
+  EV_CHARGER_TYPE_UNSPECIFIED = 0;
 
   // The EV charging station supports AC charging only.
-  EVCHARGER_TYPE_AC = 1;
+  EV_CHARGER_TYPE_AC = 1;
 
   // The EV charging station supports DC charging only.
-  EVCHARGER_TYPE_DC = 2;
+  EV_CHARGER_TYPE_DC = 2;
 
   // The EV charging station supports both AC and DC.
-  EVCHARGER_TYPE_HYBRID = 3;
+  EV_CHARGER_TYPE_HYBRID = 3;
 }
 
 // Enumerated sensor types.