migrate to patched fluent/onigmo

[edsiper]

Recently we started maintaining a stable branch of the Onigmo regex library in fluent/onigmo which includes:

• two security patches provided by the community
• new CMake support

We need to migrate the current Onigmo version to the stable one. we need to backport this too v1.9.x

[cosmo0920]

I've sent PRs for bundling cmake supported onigmo library as #6097 (For master) and #6101 (For v1.9)

[edsiper]

merged, thanks!