[MOB-10804] Rework append for better memory efficiency

[MiguelAMarcelino]

Incorporating changes submitted on this PR: jknack#1156

Trying to optimize the append method to improve memory efficiency and reduce object allocations. Previously, the code relied on the textWithoutEscapeChar method, which involved converting the internal StringBuilder to a String and then to a char[]. My goal here is to reduce unnecessary intermediate allocations and processing overhead.

Changes Introduced

• Streamlined operations to minimize the number of object switches and allocations during the append process.
• Removed textWithoutEscapeChar to avoid the conversion chain (StringBuilder → String → char[]).

Alternative Consideration:

An alternative approach considered was to rewrite the textWithoutEscapeChar method for better performance. The revised method would look like this:

public char[] textWithoutEscapeChar() {
  char[] result = new char[text.length()];
  text.getChars(0, text.length(), result, 0);
  return result;
}

This version avoids converting the StringBuilder to a String and directly copies the characters into a char[], reducing unnecessary overhead.

Future Enhancements:

There is a potential case to investigate the frequent resizing of the StringBuilder used in Text. Pre-sizing the StringBuilder to an appropriate capacity may further improve performance and memory usage.

[MiguelAMarcelino]

Closing. This has been merged on the official handlebars repo. Now its a matter of synching both.