Drop support for Unity 2019

[bitsandfoxes]

Version 2019 reached EOL mid 2022.
Apart from that there are other considerations:

• Really helps out with Rework Initialization #2227
  • No longer needing to special case a non-precompiled integration
• The usage is basically zero.
• We don't have IL2CPP support
• It's a pain to use locally as it does not seem to get along with current versions of macOS
• It's another version to support (but noone uses)
• It restricts the approach to some implementation. (I really wish I'd kept note here. Will do for 2020 which eoled 2023)

[bitsandfoxes]

This is the version used for packaging.

[bitsandfoxes]

I have not found a way to get these out of the matrix into the environment.

[bitsandfoxes]

This is actually irrelevant. Unity 2020 LTS reached its EOL in mid-2023. Specifically, the final patch version was 2020.3.48.

[bitsandfoxes]

The scene tracing can now go into the SDK itself.

[bitsandfoxes]

I've also update the packages. Previously, were using the sample project for smoke testing in CI. For that we've stripped all non-required packages to keep it as slim as possible. We're building a new smoke test project from scratch now for a while and I'd rather have the sample be the same that all users would have.

[bruno-garcia]

start with "Dropped support for Unity 2019" since this is the most importantly part of the note

[github-actions]

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