ssh: add kexAlgorithms to matchBlocks

[OliverGeneser]

Description

Add the option to specify kexAlgorithms in SSH matchBlocks.

Checklist

• Change is backwards compatible.

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[teto]

can't we make that a freeform module instead ? a la rfc42

[OliverGeneser]

can't we make that a freeform module instead ? a la rfc42

I think it should be a separate PR and this should be merge as it has already been approved.
But what do you think @khaneliman should I refactor this PR and use freeformType? Or a separate PR?

[khaneliman]

Am seeing a pattern approaching. There's a lot of customization possible with SSH and perhaps we need a refactor instead of keep shoveling in new options.

• modules/programs/ssh: support pubkeyAuthentication #8154
• ssh: add strictHostKeyChecking option #8261
• ssh: add kexAlgorithms to matchBlocks #8073