Allow users to adjust terminal transcript rows with termux.properties

This `terminal-transcript-rows` key can be used to adjust the terminal transcript rows. The user can set an integer value between `100` and `50000`. The default value is still `2000`. So adding an entry like `terminal-transcript-rows=10000` to `termux.properties` file will allow users to scroll back ~10000 lines of command output. After updating the value, termux must be restarted. You can also run `termux-reload-settings` command so that termux loads the updated value, but only new sessions will use the updated value, existing sessions will not be affected.

You can test this with the following, where `70` is number of `x` characters per line and `10001` is the number of lines to print.
`x="$(printf 'x%.0s' {1..70})"; for i in {1..10001}; do echo "$i:$x"; done`

Be advised that using large values may have a performance impact depending on your device capabilities, so use at your own risk.

Closes #2071

termux-shared/src/main/java/com/termux/shared/models/ExecutionCommand.java

@@ -81,6 +81,10 @@ public class ExecutionCommand {
     public String workingDirectory;
 
 
+    /** The terminal transcript rows for the {@link ExecutionCommand}. */
+    public Integer terminalTranscriptRows;
+
+
     /** If the {@link ExecutionCommand} is a background or a foreground terminal session command. */
     public boolean inBackground;
     /** If the {@link ExecutionCommand} is meant to start a failsafe terminal session. */