File: Re-add support to skip CR (\r) in File::get_as_text

This was removed in #63481, and we confirmed that it's better like this,
but we add back the possibility to strip CR as an option, to optionally
restore the previous behavior.

For performance this is done directly in `String::parse_utf8`.

Also fixes Android `FileAccess::get_line()` as this one _should_ strip CR.

Supersedes #63717.

tests/data/line_endings_cr.test.txt

@@ -0,0 +1 @@
+Hello darkness

tests/data/line_endings_crlf.test.txt

@@ -0,0 +1,4 @@
+Hello darkness
+My old friend
+I've come to talk
+With you again

tests/data/line_endings_lf.test.txt

@@ -0,0 +1,4 @@
+Hello darkness
+My old friend
+I've come to talk
+With you again