Release v0.4.2 (#385)

New Features:
[launcher] Add experiment support #352
[launcher] Integrate signature discovery client into attestation agent #343

Bug Fixes:
Make launcher host tmp directory before experiment fetch #363

Other Changes:
[launcher] Print kernel cmdline on builds #268
Import latest version of go-tdx-guest #373
[launcher] Print signature details instead of signature object #374
[launcher] Add image tests for the experiments binary #378
Update go-sev-guest to v0.9.3 #381