Windows port: make .exe extension implicit for |solana-install run|

[mvines]

Right now solana-install.exe run -- solana-replicator will fail here:

solana/install/src/command.rs

Lines 752 to 757 in 6926e89

	if !full_program_path.exists() {
	Err(format!(
	"{} does not exist",
	full_program_path.to_str().unwrap()
	))?;
	}

The user must instead specify solana-install.exe run -- solana-replicator.exe, which is weird for Windows users who know the .exe extension is implicit.

Let's fix this by also checking for full_program_path with .exe appended

@mvines , seems closable:

https://github.com/solana-labs/solana/blame/b997d3eb4e57728dfbd251007a6684db7c49a34c/install/src/command.rs#L899-L902

#4930

[mvines]

Oh, yep. Thanks!