CodeAction to replace deprecated `#with` into `#let` section

In the future, Qute will deprecate #with section.

We should support diagnostic and quickfix fir that:

• report a diagnostic in #with with LSP deprecated diagnostic tag.
• provide a codeaction which transform #with with #let

Given this Qute template:

{@org.acme.qute.Item item}
{#with item}
   {name}
   {price}
{/with}

#with should report a deprecated diagnostic and provide a code action to replace with:

{@org.acme.qute.Item item}
{#let name=item.name price=item.price}
   {name}
   {price}
{/let}

@mkouba what do you think about that?

Start by locating the Qute template handling for #with and the existing LSP diagnostic and code-action entry points. Add the deprecated diagnostic and a code action that transforms the example #with section into the shown #let form, then verify both results with the project's existing checks.