feat(ec2): switch to using ed25519 to generate key pair

[Hweinstock]

Problem

currently use RSA.

Solution

switch to ed25519

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License: I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

This pull request implements a feature or fix, so it must include a changelog entry. See CONTRIBUTING.md#changelog for instructions.

[justinmk3]

Always great to see tests exercising actual reality instead of setting up mocks!

[justinmk3]

This might imply that we should check the version of ssh-keygen and show an error or fallback to RSA if it doesn't support ed25519. This file has a bunch of examples using tryRun in order to sniff out whether a CLI tool supports what we expect:

aws-toolkit-vscode/packages/core/src/shared/utilities/pathFind.ts

Lines 117 to 134 in 791ae55

	export async function findSshPath(): Promise<string | undefined> {
	if (sshPath !== undefined) {
	return sshPath
	}
	const sshSettingPath = Settings.instance.get('remote.SSH.path', String, '')
	const paths = [
	sshSettingPath,
	'ssh', // Try $PATH _before_ falling back to common paths.
	'/usr/bin/ssh',
	'C:/Windows/System32/OpenSSH/ssh.exe',
	'C:/Program Files/Git/usr/bin/ssh.exe',
	]
	for (const p of paths) {
	if (!p || ('ssh' !== p && !(await fs.exists(p)))) {
	continue
	}
	if (await tryRun(p, ['-G', 'x'], 'noresult' /* "ssh -G" prints quasi-sensitive info. */)) {