runtime(java): Recognise string templates (#14150)

runtime(java): Recognise string templates (#14150)

As this is encouraged in the referenced JEPs, "to visually
distinguish a string template from a string literal, and
a text block template from a text block", the default
colours for java\%[Debug]StrTempl are made distinct from
java\%[Debug]String.

According to §3.2 Lexical Translations (JLS, c. 1996 or any
more recent version), line terminators, white space, and
comments are discarded before tokens are accepted. Since
a template expression comprises a template processor, a dot,
and a template, it may be visually appealing to break up
its head across a few lines whenever its tail already spans
multiple lines.  Curiously, no allowance for it is made in
the distributed tests for OpenJDK 21; the proposed regexp
patterns take in consideration a line terminator and white
space after a dot.

References:
https://openjdk.org/jeps/430 (Preview)
https://openjdk.org/jeps/459 (Second Preview)
https://openjdk.org/jeps/465

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>