… smaller

Ignition encodes file contents in the dataurl format. Dataurl supports
either url-escaped or base64 encoded content. CLCT always url-escapes
content, but there are cases where base64 results in smaller text. One
example is compressed content, which ignition should support but ours
doesn't due to a check which can be removed (see [1]).

So this is step 1 in enabling CLCT to transparently compress data. Data
is encoded as both url-escaped and base64 and the result lengths are
tested to see which one to use. It is possible to get CLCT to ingest
gzipped data by manually doing 'gzip+base64', using some yaml magic and
abusing CLCT parsing (slightly):

storage:
  files:
  - path: /file/path
    mode: 0644
    contents:
      remote:
        compression: gzip
      inline: !!binary |
        H4sIAAAAAAAAA8tIzcnJ5wIAIDA6NgYAAAA=

This results in spec compliant ignition configuration, that is not yet
handled by our version of the ignition program.

This is based on similar work done in butane[2].

[1]: coreos/ignition@f770885
[2]: https://github.com/coreos/butane/blob/07daeed0f1113acffbc21b47e2ecc997d44e7943/base/util/url.go#L31-L37

Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>