fundamental: move several macros and functions into src/fundamental/

sd-boot has a copy of a subset of codes from libbasic. This makes
sd-boot share the code with libbasic, and dedup the code.

Note, startswith_no_case() is dropped from sd-boot, as
- it is not used,
- the previous implementation is not correct,
- gnu-efi does not have StrniCmp() or so.

src/basic/meson.build

@@ -381,6 +381,7 @@ run_target(
 libbasic = static_library(
         'basic',
         basic_sources,
+        fundamental_sources,
         include_directories : basic_includes,
         dependencies : [versiondep,
                         threads,