Improve Coverage for Shared/Font (#2961)

Shared/Font is hardly covered in unit tests (as opposed to Style/Font which is completely covered). And it presented some good opportunities for code optimization. I wrote and tested the new unit tests first, then optimized the code and confirmed that everything still works.

There is still a bit of a gap with "exact" measurements. I had tests ready, but had to withdraw them when I discovered they weren't quite portable (see php/php-src#9073).

Author: oleibman

phpstan-baseline.neon

@@ -2270,51 +2270,6 @@ parameters:
 			count: 1
 			path: src/PhpSpreadsheet/Shared/Escher/DggContainer/BstoreContainer/BSE.php
 
-		-
-			message: "#^Cannot access offset 0 on array\\|false\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Cannot access offset 2 on array\\|false\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Cannot access offset 4 on array\\|false\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Cannot access offset 6 on array\\|false\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Parameter \\#1 \\$size of function imagettfbbox expects float, float\\|null given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Parameter \\#2 \\$defaultFont of static method PhpOffice\\\\PhpSpreadsheet\\\\Shared\\\\Drawing\\:\\:pixelsToCellDimension\\(\\) expects PhpOffice\\\\PhpSpreadsheet\\\\Style\\\\Font, PhpOffice\\\\PhpSpreadsheet\\\\Style\\\\Font\\|null given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Property PhpOffice\\\\PhpSpreadsheet\\\\Shared\\\\Font\\:\\:\\$autoSizeMethods has no type specified\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Unreachable statement \\- code above always terminates\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
-		-
-			message: "#^Variable \\$cellText on left side of \\?\\? always exists and is not nullable\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Shared/Font.php
-
 		-
 			message: "#^Property PhpOffice\\\\PhpSpreadsheet\\\\Shared\\\\JAMA\\\\EigenvalueDecomposition\\:\\:\\$cdivi has no type specified\\.$#"
 			count: 1