fix(caddyfile): {block} in snippet

[prettysunflower]

Resolve issue #7557

So, here is the situation:

• Pull request caddyfile: Allow block to do nothing if nothing passed to import #7206 included some changes to the doImport's function of Caddyfile's parser. What it does is that if there is no token within a block that follows the import, and the import contains {block}, then the {block} token is discarded.
• After this pull request:
  • Issue Index out of range error when using {block} #7518 noticed that in cases that {block} was not imported, a runtime error was raised due to the assumption that tokens were always added to tokensCopy on every iteration of importedTokens. This was fixed by pull request fix(caddyfile): Prevent parser to panic when no token were added by empty {block} #7543.
  • Issue [2.11.2 Regression] {block} is ignored when imported from a separate file #7557 notices that {block} can be ignored when imported from a certain file. There, it's again an issue with how the import works. When import snippets is called, this import instruction doesn't contains any nested blocks. And when the argument replacer that is the importedTokens loop is called and finds {block}, it uses the block from the file's import (which in this case is nothing), {block} is erased, and unavailable when the import directive is called for the imported snippet.

The changed in this commit pull request addresses the second issue by checking before replacing {block} if we're currently in a snippet definition, and appending the {block} token to tokensCopy if we are.

With this changes, when importing those snippets, the {block} token will be available to be replaced by the nested blocks in tokensToAdd if needed, or erased if there are no nested blocks and tokensToAdd is empty.

Tests added in pull requests #7206 and #7543 passes with this new implementation, confirming that unused {block} are accepted if nothing is passed to import, as well as the other usual tests. A new test was also added based on issue #7557 reporting, and also passes.

Assistance Disclosure

No AI was used. (I still wish I was a cute robot, though~)

[prettysunflower]

(Fun fact, I did a previous attempt at solving this problem by keeping the {block} tokens in context, marking them as "disposable tokens", and removing them when they were still there when all tokens were processed. This attempt is available at commit c40d7e8, though I prefer the solution submitted in this pull request for being... much simpler ^^)