ENG-74: refine credit inference regex

This commit refines the regex for inferring credit directions. It
ultimately removes requirements for names (the part after the word
"by") due to the inordinate difficulty of writing strict regex that
catches all possible characters included in names. To mitigate false
positives, it clarifies/restricts the regex for the part before the word
"by". This compromise decreases the number of false negatives without
significantly increasing false positives.

Duplicate of musescore#8678, part 3

Author: iveshenry18

importexport/musicxml/importmxmlpass2.cpp

@@ -3385,7 +3385,7 @@ bool MusicXMLParserDirection::isLikelyCredit(const Fraction& tick) const
             && _rehearsalText == ""
             && _metroText == ""
             && _tpoSound < 0.1
-            && _wordsText.contains(QRegularExpression("^\\s*((Words|Music|Lyrics).*)*by\\s+([A-Z][a-zA-Zö'’-]+\\s[A-Z][a-zA-Zös'’-]+.*)+"));
+            && _wordsText.contains(QRegularExpression("^\\s*((Words|Music|Lyrics),?(\\sand|\\s&amp;)?\\s)*[Bb]y\\s+(?!$)"));
       }
 
 //---------------------------------------------------------

mtest/musicxml/io/testInferredCredits.xml

@@ -87,13 +87,19 @@
         </attributes>
       <direction placement="above">
         <direction-type>
-          <words default-y="34.66" relative-y="10.00">Words and Music by Henry Ives
+          <words default-y="34.66" relative-y="10.00">Words &amp; Music by Henry Ives (and ampersands)
 </words>
           <words>
 </words>
           <words></words>
           </direction-type>
         </direction>
+      <direction placement="above">
+        <direction-type>
+          <words default-y="34.66" relative-y="10.00">Lyrics to be sung by candlelight
+(and this not to be inferred)</words>
+          </direction-type>
+        </direction>
       <note default-x="73.72" default-y="-15.00">
         <pitch>
           <step>C</step>

mtest/musicxml/io/testInferredCredits_ref.mscx

@@ -125,7 +125,7 @@
           </Text>
         <Text>
           <style>Composer</style>
-          <text>Words and Music by Henry Ives</text>
+          <text>Words &amp; Music by Henry Ives (and ampersands)</text>
           </Text>
         <Text>
           <style>Subtitle</style>
@@ -143,6 +143,10 @@ the video game: a tone poem</text>
             <sigN>4</sigN>
             <sigD>4</sigD>
             </TimeSig>
+          <StaffText>
+            <text>Lyrics to be sung by candlelight
+(and this not to be inferred)</text>
+            </StaffText>
           <Beam>
             <StemDirection>down</StemDirection>
             <l1>17</l1>