Switch to mostly manual release notes

[ludfjig]

Summary

This PR introduces a CHANGELOG.md file to the Hyperlight repository to systematically track and document changes. The goal is for this file to be updated with each PR that contributes to the release notes. However, in practice, it will be manually edited by the individual responsible for creating a Hyperlight release.

Motivation

The need for manual release notes arose from the limitations of our automatic release notes system. The current automatic notes were generated from PR titles, which often don't adequately reflect the changes in a manner that's easily consumable by users.

Changes

• A CHANGELOG.md file has been added to document key changes.
• The GitHub release notes will now include both the content from the CHANGELOG.md and a full list of PRs with their titles at the end of the release notes.

This approach draws inspiration from the release notes format used by Runwasi, as seen in this example.

After this merges, I will replace the old release notes in 0.2.0 with the new ones

[Mossaka]

LGTM!

[marosset]

LGTM

[marosset]

This was hit in CI on one of the Ubuntu / KVM runners but I don't see how it is related to this PR...

cargo build --profile=dev
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.17s
cargo run --profile=dev --example metrics 
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.19s
     Running `target/debug/examples/metrics`
Error: [HYPERLIGHT] Handling disallowed syscall
Error: [HYPERLIGHT] Disallowed Syscall: 257
Segmentation fault (core dumped)
error: Recipe `run-rust-examples` failed on line 168 with exit code [13](https://github.com/hyperlight-dev/hyperlight/actions/runs/13818912127/job/38660020823?pr=348#step:15:14)9

[dblnz]

lgtm

[danbugs]

Awesome stuff. LGTM

[ludfjig]

Closing because unable to merge due to unresolved comments, even though there are no unresolved comments. Reopened as #368