meson: upgrade to 1.9.1

meson: upgrade to 1.9.1

Changes in this release:

751b09390 Bump versions to 1.9.1 for release
d0abb2133 Boost python must have a library component.
e6732c220 Check for header only Boost libraries.
08429813b get_llvm_tool_names: add llvm 21
f3b383217 docs: fix pre-1.8 order for per-subproject options
a2d395498 Revert "test cases: do not pass global option on command line"
d0f82544e Revert "tests: skip test common/223 in the -Ddefault_library=... jobs"
2abdb2f0b options: put back in place 1.7 ordering of opt=value vs subp:opt=value
83cbc65c2 Fix not passing user option args to scan-build build
e746db0b4 Document internal dep support in pkgconfig.generate `requires` arg
f6ab732b7 msetup: not-found subprojects do not have known options
5d21e653a utils: make .wraplock optional
d1e219cb8 Fix Cygwin test failure.
0fc77e2d7 coredata: do not write None to cmd_line.txt
533ba5cb3 options: do not raise exception for unknown options in -U command
ae822d1d4 test cases/common/32 has header: disable undef with libcxx
c58f0d951 rustdoc: skip --crate-type option
b8e0e9d3d fix transient failure on rust/12 bindgen
75cf757b7 coredata: check for per-subproject compiler and linker arguments
a747c4ea8 coredata: check for per-subproject compiler options

Drop the two backported patches.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>