Change default TLS stack to rustls-tls

[clux]

Motivation

Want to encourage the use of the more secure and robust TLS stack by default.
Based on feedback (see e.g. #1192) and personal experience have not seen or heard about any current issues.
The main blocker bug was resolved some months ago
This also allows us to not have a huge windows hack in our windows CI.

Solution

• switch our explicit default to feature to kube/rustls-tls
• switch our precedence when both features are enabled to rustls-tls
• make windows run tests in the same way as other platforms

As a clean-up while in the area, have also prevented erroneous Client construction on a TLS requiring cluster, when TLS stacks are disabled. That caused an ugly freezen in #1275

[codecov]

Codecov Report

Merging #1261 (90040bd) into main (259ed96) will decrease coverage by 0.15%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1261      +/-   ##
==========================================
- Coverage   72.44%   72.30%   -0.15%     
==========================================
  Files          75       75              
  Lines        6337     6347      +10     
==========================================
- Hits         4591     4589       -2     
- Misses       1746     1758      +12     

Files Changed	Coverage Δ
kube-client/src/client/auth/oauth.rs	0.00% <ø> (ø)
kube-client/src/client/auth/oidc.rs	57.24% <ø> (ø)
kube-client/src/client/builder.rs	71.42% <100.00%> (+0.51%)	⬆️

... and 4 files with indirect coverage changes

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[aviramha]

Exciting!!
Need to update the README.md

By default openssl is used for TLS, but rustls is supported. To switch, turn off default-features, and enable the rustls-tls feature:

[clux]

Getting ready to push this in as it is getting close to release time.

Some quick testing on no-tls feature against tls clusters now gives:

WARN kube_client::client: Unsuccessful data error parse: Client sent an HTTP request to an HTTPS server

maybe that should be promoted to a harder error also, ill look later

EDIT: ok this doesn't happen in all cases. on my k3d where auth layer is set we properly get a hard error:

Error: TLS required but no TLS stack selected

this is testable with turning off rustls + refresh feature in examples/Cargo.toml (but keeping client)

but am seeing it on a rancher cluster where the auth is just user.token: some-kubeconfig-uid. in this case we can detect it with cluster.server url being https scheme. EDIT2: fixed.