protolint: configure protolint and fix the protolinting issues

This PR addresses the following:
- Install and Configure protolint to enforce the protobuf style guide rules in the CI.
- Fix the protolinting issues (package and import ordering) while maintaining the comaptibility.

.protolint.yaml

@@ -0,0 +1,70 @@
+# The example configuration file for the protolint is located here:
+# https://github.com/yoheimuta/protolint/blob/master/_example/config/.protolint.yaml
+---
+# Lint directives.
+lint:
+  # Linter rules.
+  # Run `protolint list` to see all available rules.
+  rules:
+    # Determines whether or not to include the default set of linters.
+    no_default: true
+
+    # Set the default to all linters. This option works the other way around as no_default does.
+    # If you want to enable this option, delete the comment out below and no_default.
+    # all_default: true.
+
+    # The specific linters to add.
+    add:
+      - MESSAGE_NAMES_UPPER_CAMEL_CASE
+      - MAX_LINE_LENGTH
+      - INDENT
+      - FILE_NAMES_LOWER_SNAKE_CASE
+      - IMPORTS_SORTED
+      - PACKAGE_NAME_LOWER_CASE
+      - ORDER
+      - SERVICES_HAVE_COMMENT
+      - RPCS_HAVE_COMMENT
+      - PROTO3_FIELDS_AVOID_REQUIRED
+      - PROTO3_GROUPS_AVOID
+      - SYNTAX_CONSISTENT
+      - RPC_NAMES_CASE
+      - QUOTE_CONSISTENT
+
+  # Linter rules option.
+  rules_option:
+    # MAX_LINE_LENGTH rule option.
+    max_line_length:
+      # Enforces a maximum line length.
+      max_chars: 80
+      # Specifies the character count for tab characters.
+      tab_chars: 2
+
+    # INDENT rule option.
+    indent:
+      # Available styles are 4(4-spaces), 2(2-spaces) or tab.
+      style: 4
+      # Specifies if it should stop considering and inserting new lines at the appropriate positions.
+      # when the inner elements are on the same line. Default is false.
+      not_insert_newline: true
+
+    # QUOTE_CONSISTENT rule option.
+    quote_consistent:
+      # Available quote are "double" or "single".
+      quote: double
+
+    # ENUM_FIELD_NAMES_ZERO_VALUE_END_WITH rule option.
+    enum_field_names_zero_value_end_with:
+      suffix: INVALID
+
+    # SERVICE_NAMES_END_WITH rule option.
+    service_names_end_with:
+      text: Service
+
+    # REPEATED_FIELD_NAMES_PLURALIZED rule option.
+    ## The spec for each rules follows the implementation of https://github.com/gertd/go-pluralize.
+    ## Plus, you can refer to this rule's test code.
+    repeated_field_names_pluralized:
+      uncountable_rules:
+        - paper
+      irregular_rules:
+        Irregular: Regular