* track nim-libp2p's unstable branch and nim-bearssl's master branch
refactor accordingly: mainly switching from `import bearssl` to
`import bearssl/rand`, `BrHmacDrbgContext` to `HmacDrbgContext`, and related
changes
* fix ambiguous identifier
* nim 1.4 is deprecated
Co-authored-by: Michael Bradley, Jr <michaelsbradleyjr@gmail.com>