[SSR] Avoid variable name collisions on `tmpl`, `generateMarkup`, etc.

[nolanlawson]

If a component author does something like the following:

import { LightningElement } from 'lwc';

const tmpl = undefined;
const generateMarkup = undefined;

export default class extends LightningElement {
    connectedCallback() {
        // just use the variables to avoid them being tree-shaken
        Object.assign(
            {},
            {
                tmpl,
                generateMarkup
            }
        );
    }
}

Then currently, it will throw an error at compile time in the @lwc/ssr-compiler:

Identifier "tmpl" has already been declared
Identifier "generateMarkup" has already been declared

These are pretty generic names, so we should probably switch to something like __lwcTemplate and __lwcGenerateMarkup to avoid collisions.

Related:

• [SSR] SSR v2 scoped slots should handle variable names like generateMarkup #4768
• fix(ssr): avoid reserved keyword collision #5108

[git2gus]

This issue has been linked to a new work item: W-17561326