AB#2173: Add feature to bundle a signed executable with the current EGo runtime

[Nirusu]

Proposed changes

• Add a new binary called 'ego-bundle', which is a self-extractable runtime
• Add 'ego bundle' CLI command which bundles a signed EGo executable into the 'ego-bundle' binary and create a copy of it
• Unit tests for both of them (including some host I/O, but I tried to limit it to where its necessary)

Additional info

For this PR I am not sure where to draw the line for code reuse. Many parts, especially for the unit tests are copied from the CLI or main EGo package to avoid calling NewCLI, though it is essentially the same code. On the other hand, I also was not sure whether to create an internal package to re-use functions, given that the bundle executable is supposed to pretty much stand on its own... I don't know, let me know in the review about your opinions.

Also don't be scared about the # of lines added, there's more test code involved than the actual functionality :)

[Nirusu]

Ready for re-review. I merged the common code from cli and bundle into internal/launch. I also put the untar logic in there, given that it is kinda launch related and I did not want to create yet another utils package just for one function.

Also, for the output filename I did go the hybrid way: If no output name is specified, take the original name and append "-bundle", otherwise use the specified output name.

I also separated the "utils.go" I created before into separate files that are more distinctive. That should look better and make more sense I believe.

[Nirusu]

Sorry for all the additional commits. I now also completely moved the Marblerun launch to the internal package, so that cli/run.go really mainly is a caller around the new launch package. That's mainly just for consistency, so that all launch commands are at one place, even if the CLI is so far the only caller for the Marblerun launch mode.

[thomasten]

Nice work, thanks!