chore: migrate GTM snippet to amplitude-typescript

[daniel-graham-amplitude]

Summary

The goal of this PR is to deprecate https://github.com/amplitude/amplitude-js-gtm/ in favour of having the GTM code snippet being deployed in amplitude-typescript, alongside analytics-browser

In this PR

• Added an EJS template for amplitude-wrapper that takes the contents of the analytics-browser and plugin-session-replay-browser scripts and puts them into "amplitude-wrapper.js" (similar how we did in amplitude-js-gtm)
• Added a rollup script that takes the js file that's generated above, and then gzips it
• Added a test page to the test-server that runs a test on the above gzipped page
• Set the version of the new script to be the same as "analytics-browser" so that they are always released concurrently

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: No

[Mercy811]

Set the version of the new script to be the same as "analytics-browser" so that they are always released concurrently

Do you mean to set the new package @amplitude/gtm-snippet the same version as @amplitude/analytics-browser? This is a good idea! So that we don't need to map event library version (wrapper version) to the actual SDK version. And there is no requirement to start a npm package from 1.0.0.

[Mercy811]

Thanks @daniel-graham-amplitude, LGTM!