fix(website): render code config examples as code blocks

[pront]

Summary

Component reference pages render each field's example through jsonify, which escapes newlines
to a literal \n. Fields whose value is a program — VRL (remap's source) or Lua (the lua
transform's hooks) — therefore showed their multi-line examples as one run-together escaped
string. This drives example rendering off the field's declared syntax: code syntaxes render as
a highlighted code block with newlines intact, everything else stays inline. Doing it declaratively
via syntax avoids brittle content-sniffing and extends to any code-valued field with a single
map entry.

Changes

• config-examples renders a field's examples as a highlighted code block when its syntax is a
  source-code type, via a syntax → lexer map (vrl_program → coffee, lua → lua, yaml,
  toml); every other syntax renders inline as JSON.
• Renamed the remap_program syntax to vrl_program (the language is VRL, not "remap").
• Marked the lua transform's program and hook fields with syntax: lua so their examples render
  as code too.

How did you test this PR?

• Built the docs locally and confirmed the remap source (VRL) and the lua hook examples now
  render as multi-line code blocks, while non-code examples — e.g. the file source's \r\n
  delimiter — stay inline.

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Related: enhancement(remap): unify VRL source configuration #25948

[datadog-vectordotdev]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

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