Show installed toolchains if a user tries to set an incorrect toolchain name to the default. #1982

Job	Run time
cancel-previous-runs	3s
cargo-clippy	18s
check-scripts	15s
cargo-test-workspace	1m 6s
cargo-fmt-check	13s
lint-toml-files	16s
build fuelup release binaries	0s
Try fuelup installation with fuelup-init (ubuntu-latest)	15s
Try fuelup installation with fuelup-init (macos-latest)	20s
Do post-release checks	0s
publish-check	0s
	2m 46s

Provide feedback