[text-spacing-trim] Add ShapeOptions::is_line_start

When re-shaping line-start, it shouldn't take the previous
character into account for `HanKerning`.

This patch adds `ShapeOptions::is_line_start` to let
`HanKerning` know if its start is line-start, and change
callers to set the option.

Bug: 1463891
Change-Id: I52e70d7e725d5d8be3838180fae11213c510cf97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5210010
Commit-Queue: Kent Tamura <tkent@chromium.org>
Auto-Submit: Koji Ishii <kojii@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1249211}

css/css-text/text-spacing-trim/text-spacing-trim-start-001-ref.html

@@ -10,6 +10,7 @@
  font-family: halt-font;
  font-size: 20px;
  inline-size: 4em;
+ text-spacing-trim: space-all;
 }
 .vrl {
  writing-mode: vertical-rl;
@@ -26,6 +27,7 @@
 </style>
 <div id="container">
  <div><ps>（</ps>国国国<ls>（</ls>国国国<ls>（</ls>国</div>
+ <div>国国国）<ls>（</ls>国国）<ls>（</ls>国</div>
  <div>国国国国<ls>（</ls></div>
  <div lang="zh-hans">国国国国<ls>“</ls></div>
 

css/css-text/text-spacing-trim/text-spacing-trim-start-001.html

@@ -44,6 +44,7 @@
 </style>
 <div id="container">
  <div>（国国国（国国国（国</div>
+ <div>国国国）（国国）（国</div>
  <div>国国国国（</div>
  <div lang="zh-hans">国国国国“</div>