bugfix: fix push option (#100)

* `push`:
  * Use `pdk_family` instead of `pdk` (was overlooked in #96) 
  * Set default owner/repo to fossi-foundation/ciel-releases
* `git_multi_clone`:
* Set `text=True` in `subprocess.Popen` to always use the correct locale
for git

hotfix: --pdk not getting returned

feat!: skyfall (#96)

* CLI: `--pdk` renamed to `--pdk-family` (with old flag as an alias)
* Custom click validator ensures that the PDK family is valid (and if
not provided, prints a list of supported PDKs)
* Default value removed: PDK now has to always be explicitly specified
and sky130 is no longer given preferential treatment

---------

Co-authored-by: Mohamed Gaber <[email protected]>

fetch: rework to use data sources (#95)

Introduces the concept of a DataSource to Ciel, an abstraction of remote
data repositories. There are two concrete implementations thereof:

* GitHubReleasesDataSource: Which uses GitHub Releases, effectively
behaving identically to Volare.
* StaticWebDataSource: Which uses a static webpage to fetch manifest
files that replace the API calls in questions.

Users can provide the data source over the command-line using
`--data-source {class}:{argument}`, where class can be `github-releases`
or `static-web` respectively. When the data source is `github-releases`,
the argument is in the format '{owner}/{repo}', and when the data source
is a static website, the argument is a URL to the base directory where
the manifest files are located. The manifest files are free to point to
any file on the internet for download information.

The default data source is
`static-web:https://fossi-foundation.github.io/ciel-releases`. To act
identically to Volare, the data source can be
`github-releases:efabless/volare`.

ci: update secret name

hotfix: minor logic bug

hotfix: rename ihp default variant to prevent setup files from breaking

hotfix: rename ihp-sg13g2, replace `-` with `_`

Multiple dashes in a release name break `ls-remote` in every previous version of Volare.

hotfix: ignore .git directories in submodules

hotfix: include submodules for IHP builds