Qt: Disambiguate offset direction labels from DPad/Stick labels (#18695)

## Summary

The "Left" and "Right" strings in `pad_settings_dialog` were shared
between DPad/Stick direction labels (which have ample space) and offset
value labels — Squircle Values, Stick Multipliers, and Stick
Interpolation (where space is tight). Translators couldn't abbreviate
the offset version without also affecting the direction binding labels.

## Change

Added disambiguation via `comment="Offset direction"` in the `.ui`
file's `<string>` elements for the six offset labels:

- `label_squircle_left`
- `label_squircle_right`
- `label_stick_multi_left`
- `label_stick_multi_right`
- `left_stick_lerp_label`
- `right_stick_lerp_label`

Qt now generates separate translation entries, allowing translators to
use shorter abbreviations in the tight offset areas while keeping full
forms for direction bindings.

**English UI is unchanged** — no visual difference for English users.

Fixes #18691

rpcs3/rpcs3qt/pad_settings_dialog.ui

@@ -2348,7 +2348,7 @@
                <item>
                 <widget class="QLabel" name="label_squircle_left">
                  <property name="text">
-                  <string>Left</string>
+                  <string comment="Analog stick">Left</string>
                  </property>
                 </widget>
                </item>
@@ -2378,7 +2378,7 @@
                <item>
                 <widget class="QLabel" name="label_squircle_right">
                  <property name="text">
-                  <string>Right</string>
+                  <string comment="Analog stick">Right</string>
                  </property>
                 </widget>
                </item>
@@ -2429,7 +2429,7 @@
                <item>
                 <widget class="QLabel" name="label_stick_multi_left">
                  <property name="text">
-                  <string>Left</string>
+                  <string comment="Analog stick">Left</string>
                  </property>
                 </widget>
                </item>
@@ -2456,7 +2456,7 @@
                <item>
                 <widget class="QLabel" name="label_stick_multi_right">
                  <property name="text">
-                  <string>Right</string>
+                  <string comment="Analog stick">Right</string>
                  </property>
                 </widget>
                </item>
@@ -2673,7 +2673,7 @@
                    <item>
                     <widget class="QLabel" name="left_stick_lerp_label">
                      <property name="text">
-                      <string>Left</string>
+                      <string comment="Analog stick">Left</string>
                      </property>
                     </widget>
                    </item>
@@ -2703,7 +2703,7 @@
                    <item>
                     <widget class="QLabel" name="right_stick_lerp_label">
                      <property name="text">
-                      <string>Right</string>
+                      <string comment="Analog stick">Right</string>
                      </property>
                     </widget>
                    </item>