Add optional erasable syntax configuration to Typescript generator.

[brendandburns]

Typescript 5.8 added a new flag that optionally removes support for non-erasable syntax. This facilitates running Typescript directly in node 22 without transpiling. This PR adds a new configuration option to the Typescript generator to generate code that complies with erasable syntax only. It is off by default.

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[amakhrov]

Is there a reason not to ALWAYS generate erasable syntax, without extra configuration and complexity in the templates?

[brendandburns]

@amakhrov

Personally, I'm ok with that, but I made it optional because I wanted to minimize the potential impact to users of this generator.

[joscha]

I think having both options is quite the onus on future implementers and maintainers. You always have to think about both cases and what's supported might change over time as well as ecmascriot evolves, etc.

Given that we want to run future versions of this on native node, I personally would go with one of two options:

• Always produce erasable syntax
• Flick the switch to default yes for now, so all test fixtures are produced with erasable syntax and then we add node into CI to ensure we're compatible. Given that erasable syntax is always compatible with non-erasable, that seems to be the safer bet overall. Then, in the near future, I don't know, 7.13 or something, we remove the old code path.

Thoughts?

[brendandburns]

@joscha I'm fine with either option. I defer to the various typescript technical committee members opinion. Let me know the preferred solution and I will implement it in this PR.

[joscha]

@amakhrov @macjohnny thoughts?

[topce]

@brendandburns I like what you done: to be optional and by default working like before
not sure all users target latest version of node...
LGTM as it is.