Escaping index name when creating a snapshot

[mateuszkaczynski]

In some cases the index name might not play well with the file system of the snapshot repository.

For example, trying to snapshot 'index_crawl:1' (which includes a colon) would fail in for plugins using URI-based filesystems (HDFS for example) due to filesystem restrictions.

[clintongormley]

@imotov is this already implemented, or do we still need to do it?

[imotov]

No, we will just use index name as is (which means we will only observe the index name restrictions).

[imotov]

This is getting addressed as part of a bigger changes in snapshot/restore file naming schema in #18156. So, I am going to close it here.