## What changed?
<!-- Describe what has changed in this PR -->
Remove license header from every file. Because it is really hard to
follow in this PR here is the summary:
1. License header is removed from all `.go` and `.proto` files
:fireworks::fireworks:🎆.
2. `LICENSE` file in the root directory has only Temporal and Uber
copyrights.
3. 5 other `LICENSE` files added to the packages which have copyrights
different from Temporal and Uber: Datadog, Xargin, "Mat Ryer, Tyler
Bunnell and contributors".
4. `license_file` flag is removed from all code generation tools.
5. `copyright_file` flag is removed from `go:generate mockgen`
directive.
6. All copyright related targets are removed from `Makefile`.
7. Updated Temporal copyright year to 2025 everywhere.
## Why?
<!-- Tell your future self why have you made these changes -->
I double checked with legal department that it is not needed to have
license header in every file. One file per repo is enough. I put all
copyrights to the root `LICENSE` file and removed header from all other
files. Also updated tools and `Makefile`.
## What changed?
<!-- Describe what has changed in this PR -->
Moved all packages inside `/internal` to `/common`.
## Why?
<!-- Tell your future self why have you made these changes -->
While the `internal` package provides the benefit of preventing any
external party from depending on them, we find that in practice this has
little benefit.
Our compatibility guarantees do not coverage any APIs in `common`
anyway.
Furthermore, splitting commonly-used packages into two places hinders
discoverability. And adds (albeit minor) mental friction.
## How did you test it?
<!-- How have you verified this change? Tested locally? Added a unit
test? Checked in staging env? -->
Compiler.
## Potential risks
<!-- Assuming the worst case, what can be broken when deploying this
change to production? -->
External users could start relying on these packages. But that's their
risk assessment to make. There are no guarantees (just like for any
other package in this repo!) outside of the external APIs.
## Documentation
<!-- Have you made sure this change doesn't falsify anything currently
stated in `docs/`? If significant
new behavior is added, have you described that in `docs/`? -->
## Is hotfix candidate?
<!-- Is this PR a hotfix candidate or does it require a notification to
be sent to the broader community? (Yes/No) -->
