[FIX] *: fix css issue with labels in Settings page

Settings page lacks a space between some labels and corresponding selection
input. Example: label *Digest Email* and default value *Your Odoo Periodic
Digest*.

Fix it by adding margin via mr8 class

Code analysis
=============

v15 has margin:
https://github.com/odoo/odoo/blob/eee0a77619b0cef70272b24f6ff663210e94eb1e/addons/web/static/src/legacy/scss/form_view.scss#L673

while v16 doesn't have it
https://github.com/odoo/odoo/blob/3ee5d7a0fbccae5f742e1aba8d3d24f8bab3cbdd/addons/web/static/src/views/form/form_controller.scss#L605

v16 was refactored first https://github.com/odoo/odoo/commit/8fa6e923d0fc8695d92e0b114e230d3abab7d9bc

- margin: 0 $o-form-spacing-unit 0 0;
+ margin-right: $o-form-spacing-unit;

but then it was completely removed
https://github.com/odoo/odoo/commit/fb629dc91df1720cb0658d3e9f946a4fda83fbd0



opw-3115232

closes odoo/odoo#114300

Related: odoo/enterprise#38499
Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>

addons/auth_password_policy/views/res_config_settings_views.xml

@@ -10,7 +10,7 @@
                 <div class="col-12 col-lg-6 o_setting_box">
                     <div class="o_setting_left_pane"/>
                     <div class="o_setting_right_pane">
-                        <label for="minlength"/>
+                        <label for="minlength" class="mr8"/>
                         <field name="minlength"/>
                     </div>
                 </div>

addons/digest/views/res_config_settings_views.xml

@@ -23,7 +23,7 @@
                                 </div>
                                 <div class="content-group" attrs="{'invisible': [('digest_emails','=',False)]}">
                                     <div class="mt16">
-                                        <label for="digest_id" class="o_light_label"/>
+                                        <label for="digest_id" class="o_light_label mr8"/>
                                         <field name="digest_id" class="oe_inline"/>
                                     </div>
                                     <div class="mt8">

addons/stock_landed_costs/views/res_config_settings_views.xml

@@ -9,7 +9,7 @@
             <div name="landed_cost_info" position="replace">
                 <div class="content-group" attrs="{'invisible': [('module_stock_landed_costs', '=', False)]}">
                     <div class="mt16">
-                        <label for="lc_journal_id" string="Default Journal"/>
+                        <label for="lc_journal_id" class="mr8" string="Default Journal"/>
                         <field name="lc_journal_id"/>
                     </div>
                 </div>

addons/website_event_jitsi/views/res_config_settings_views.xml

@@ -8,7 +8,7 @@
             <xpath expr="//div[@name='events_setting_container']" position="inside">
                 <div class="col-12 col-lg-6 o_setting_box">
                     <div class="o_setting_right_pane">
-                        <label for="jitsi_server_domain"/>
+                        <label for="jitsi_server_domain" class="mr8"/>
                         <field name="jitsi_server_domain" placeholder="meet.jit.si"/>
                     </div>
                 </div>