RFR: 7903727: Remove the reliance on String Templates feature [v9]

[Nizar Benalla]

> This PR aims to replace the usage of string templates with `String::format`, since there will be no string template feature in JDK 23.
> I tried to keep similar indentation and convert them in-place, to make reviewing the changes easier.

Nizar Benalla has updated the pull request incrementally with one additional commit since the last revision:

  -create a new `format` method
  -fix some indetation/spaces

-------------

Changes:
  - all: https://git.openjdk.org/jextract/pull/244/files
  - new: https://git.openjdk.org/jextract/pull/244/files/32a3b6cd..fae689a3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=244&range=08
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=244&range=07-08

  Stats: 10 lines in 2 files changed: 4 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jextract/pull/244.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/244/head:pull/244

PR: https://git.openjdk.org/jextract/pull/244