FIPS support

A discussion I just had with @tehbooom highlighted the need many customers have for a FIPS-compliant binary build if they intend to use the CLI in their environments.

Our current experimental binary builds (see the downloadable bins on [the 0.4.0 release page](https://github.com/elastic/cli/releases/tag/v0.4.0)) are generated using Bun, because it was simpler to achieve, and the resulting binaries run a bit faster than an equivalent binary generated by Node.js (see [this comment](https://github.com/elastic/cli/pull/546#issuecomment-5330027315) for general notes on comparative benchmarks).

Unfortunately, [Bun does not yet support FIPS](https://github.com/oven-sh/bun/issues/4869) so for compliance we would need to switch back to Node.js for binary builds. We'll also need to identify what kind of environment is required, such as a chainguard image and Node.js built with a FIPS-approved SSL stack. More research will be needed to establish the correct way to do this.

Start by reviewing the experimental binaries on the 0.4.0 release page, the linked Bun FIPS issue, and the benchmark notes in PR #546. Determine the required build environment, including whether a Chainguard image and FIPS-approved Node.js SSL stack are needed. Done means the project has an established path to producing a FIPS-compliant CLI binary.

Written by the indexing model from the issue text.