New Rule: svelte/no-dupe-on-directives and svelte/no-dupe-use-directives

[ota-meshi]

Motivation

We can define any number of on: and use: directives with the same name, but duplicate directives with the exact same name and expression are probably a mistake.
I would like to find it in the new rule.

See also sveltejs/svelte#8048.

Description

The new rule reports on: directives with exactly the same name and expression, and use: directives with exactly the same name and expression.

Examples

<!-- ✓ GOOD -->
<button on:click on:click={myHandler}  />
<button on:click={foo} on:click={bar}  />
<div use:clickOutside use:clickOutside={param}  />
<div use:clickOutside={foo} use:clickOutside={bar} />

<!-- ✗ BAD -->
<button on:click on:click />
<button on:click={myHandler} on:click={myHandler} />
<div use:clickOutside use:clickOutside  />
<div use:clickOutside={param} use:clickOutside={param}  />

Additional comments

As for on:, maybe some users want to report even if the expression is different. I think we can add an option to the rule in that case.

<!-- maybe BAD? -->
<button on:click={foo} on:click={bar}  />

<!-- GOOD? -->
<script>
function handler(evt) {
  foo(evt);
  bar(evt);
}
</script>
<button on:click={handler} />