XFA - Fix text positions (bug 1718741)

- font line height is taken into account by acrobat when it isn't with masterpdfeditor: I extracted a font from a pdf, modified some ascent/descent properties thanks to ttx and the reinjected the font in the pdf: only Acrobat is taken it into account. So in this patch, line heights for some substituted fonts are added.
  - it seems that Acrobat is using a line height of 1.2 when the line height in the font is not enough (it's the only way I found to fix correctly bug 1718741).
   - don't use flex in wrapper container (which was causing an horizontal overflow in the above bug).
   - consequently, the above fixes introduced a lot of small regressions, so in order to see real improvements on reftests, I fixed the regressions in this patch:
     - replace margin by padding in some case where padding is a part of a container dimensions;
     - remove some flex display: some containers are wrongly sized when rendered;
     - set letter-spacing to 0.01px: it helps to be sure that text is not broken because of not enough width in Firefox.

test/pdfs/xfa_bug1718741.pdf.link

@@ -0,0 +1 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=9229375

test/test_manifest.json

@@ -960,6 +960,14 @@
        "enableXfa": true,
        "type": "eq"
     },
+    {  "id": "xfa_bug1718741",
+       "file": "pdfs/xfa_bug1718741.pdf",
+       "md5": "1b80f8287cdbf9a67e4bff8be20b1bbd",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
     {  "id": "xfa_bug1718670_1",
        "file": "pdfs/xfa_bug1718670_1.pdf",
        "md5": "06745be56a89acd80e5bdeddabb7cb7b",

test/unit/xfa_tohtml_spec.js

@@ -126,7 +126,7 @@ describe("XFAFactory", function () {
         fontStyle: "normal",
         fontWeight: "normal",
         fontSize: "6.93px",
-        margin: "1px 4px 2px 3px",
+        padding: "1px 4px 2px 3px",
         verticalAlign: "2px",
       });