v2.1: use create_and_canonicalize_directory for snapshots dir (backport of #3923)

[mergify]

Problem

we don't create "snapshots" dir for users before we canonicalize.

Summary of Changes

do something similar with ledger path:

agave/validator/src/main.rs

Lines 997 to 1004 in df27fb3

	let ledger_path = create_and_canonicalize_directories([&ledger_path])
	.unwrap_or_else(|err| {
	eprintln!(
	"Unable to access ledger path '{}': {err}",
	ledger_path.display(),
	);
	exit(1);
	})

---

This is an automatic backport of pull request #3923 done by [Mergify](https://mergify.com).

[yihau]

the main reason for this bp is that it's a patch for this bug:

when we run agave-validator --snapshots SNAPSHOTS_PATH_THAT_DOES_NOT_EXIST ..., it canonicalizes the path directly without creating dirs for non-existent paths. it will report you something like:

Failed to canonicalize snapshots path '/home/sol/ledger-snapshots': No such file or directory (os error 2)

[bw-solana]

LGTM

[steviez]

LGTM