tclPackages: init

[fgaz]

Motivation: https://discourse.nixos.org/t/a-tcl-package-set/28071

A successor of #235614 with two key differences:

• I added a by-name hierarchy.
• I removed versioned sets. We can instead rely on the stubs mechanism (between minor versions at least). Versioned sets can be added later if we we find they are needed.

The treewide migration of existing packages is its own commit to make review easier.

To do:

• Finish moving packages to tcl-modules
• Documentation
• Enable stubs on applicable packages. Let's do this later so we avoid rebuilds in this PR.

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Pinging people who expressed interest in this: @infinisil @nat-418 @andreabedini
Pinging the tcl maintainer: @agbrooks

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Note

ofborg will report some rebuilds because of the change in attrpaths, however the store hashes are the same. This pr should cause 0 actual rebuilds

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/a-tcl-package-set/28071/10

[fgaz]

@agbrooks thanks!

Tcl packages are being updated because of the recent 9.0 release, so conflicts are likely. Most other review requests are due to all the renames, so I will add a a changelog entry and merge this pr on Friday unless there are objections.