Comment box tweaks and SVG dropdown triangles (#13376)

* Comment box tweaks and SVG dropdown triangles

- Change all dropdown triangles to SVG
- Bring inline review comment box closer to regular comment boxes
- Enhance arc-green checkbox contrast
- Minor reaction tweaks
- Flexbox the diff file header

* remove a border

* fix type marker in arc-green

* add small code padding

* fix position regression and remove useless rules

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

templates/admin/auth/source/ldap.tmpl

@@ -4,7 +4,7 @@
 		<div class="ui selection security-protocol dropdown">
 			<input type="hidden" id="security_protocol" name="security_protocol" value="{{.security_protocol}}">
 			<div class="text">{{.CurrentSecurityProtocol}}</div>
-			<i class="dropdown icon"></i>
+			{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 			<div class="menu">
 				{{range .SecurityProtocols}}
 					<div class="item" data-value="{{.Type}}">{{.Name}}</div>

templates/admin/auth/source/oauth.tmpl

@@ -4,7 +4,7 @@
 		<div class="ui selection type dropdown">
 			<input type="hidden" id="oauth2_provider" name="oauth2_provider" value="{{.oauth2_provider}}">
 			<div class="text">{{.oauth2_provider}}</div>
-			<i class="dropdown icon"></i>
+			{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 			<div class="menu">
 				{{range $key, $value := .OAuth2Providers}}
 					<div class="item" data-value="{{$key}}">{{$value.DisplayName}}</div>

templates/admin/auth/source/smtp.tmpl

@@ -4,7 +4,7 @@
 		<div class="ui selection type dropdown">
 			<input type="hidden" id="smtp_auth" name="smtp_auth" value="{{.smtp_auth}}">
 			<div class="text">{{.smtp_auth}}</div>
-			<i class="dropdown icon"></i>
+			{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 			<div class="menu">
 				{{range .SMTPAuths}}
 					<div class="item" data-value="{{.}}">{{.}}</div>

templates/admin/auth/source/sspi.tmpl

@@ -29,7 +29,7 @@
 		<label for="sspi_default_language">{{.i18n.Tr "admin.auths.sspi_default_language"}}</label>
 		<div class="ui language selection dropdown" id="sspi_default_language">
 			<input name="sspi_default_language" type="hidden" value="{{.SSPIDefaultLanguage}}">
-			<i class="dropdown icon"></i>
+			{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 			<div class="text">{{range .AllLangs}}{{if eq $.SSPIDefaultLanguage .Lang}}{{.Name}}{{end}}{{end}}</div>
 			<div class="menu">
 				<div class="item{{if not $.SSPIDefaultLanguage}} active selected{{end}}" data-value="">-</div>