fix: remove Rust related scripts and doc update

[Revolyssup]

Description

This is a follow up PR to #9936 and removes mentions of RUST from docs as well as remove the scripts that install and check for rust.

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[shreemaan-abhishek]

Please remove this as well:

apisix/t/chaos/utils/Dockerfile

Lines 39 to 43 in 35349ef

	&& curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sudo sh -s -- -y \
	&& source "$HOME/.cargo/env" \
	&& export CARGO_REGISTRIES_CRATES_IO_PROTOCOL=sparse \
	# next line is for rust cdylib compile on musl
	&& export RUSTFLAGS="-C target-feature=-crt-static" \

[Revolyssup]

@shreemaan-abhishek done