* Update and fix bcftools package

This PR updates bcftools to 1.10.2 and is dependent on PR #14504.

This PR also fixes builds of other versions. Versions 1.2-1.4 did not
use autotools so when the packaeg was converted to use autotools with
version 1.6 those older versions could no longer build. Also, those
versions needed to be patched to use an external htsllib. The method of
finding the external htslib is also different for those older versions.

In addition, this PR adds two variants to bcftools:

- libgsl
- perl-filters

Finally, dependencies for perl and python are added, and an unused
dependency for libzip was removed.

* Do not use '@' in variant description

The '@' character in a variant description will cause a problem with
`spack info`.

```
==> Error: Incomplete color format: '@' in
expressions, for @1.8:
```

* Fix error with python2 processing this package