wasi-libc: remove crt1.o as it's not WASI ABI compatible

[kubkon]

According to WASI ABI spec, the assumed exec model for a WASI module can either be a command or a reactor. The former then uses crt1-command.o and the latter crt1-reactor.o when linking with wasm-ld. This therefore obsoletes the need for building and linking crt1.o especially as #9178 landed in master.

Tweaks necessary to the codebase:

• remove lib/libc/wasi/libc-bottom-half/crt/crt1.c
• remove crt1_o variant in src/wasi_libc.zig and any prong that would lead to it plus const crt1_src_file = "wasi/libc-bottom-half/crt/crt1.c";