maint: bump copyright dates to 2023

[praiskup]

Processed by command: $ make UPDATE_COPYRIGHT_SCRIPT=/gnulib/build-aux/\ update-copyright update-copyright

• LICENSE, Makefile, build-aux/bootstrap.in, build-aux/extract-trace, build-aux/funclib.sh, build-aux/inline-source, build-aux/options-parser, tests/test-all-shells.sh, tests/test-funclib-quote.sh, tests/test-option-parser-helper, tests/test-option-parser.sh: Bump copyright to include 2023.
• bootstrap: Regenerate.