chore(core): add script action for rebuilding ldml header and move ts from core to common 🙀

It is best if we don't have deep deps on core/include/ldml for ts builds. So move the relevant files into common/ somewhere. (This is a bit recursive as well at present because kmc depends on core/include/ldml, but core depends on kmc for building tests, and this change would fix that.)

The .ts file should be a part of common/web/types. The .h file should go in /common/include (and should be .gitignored). ldml-const-builder should go in /common/tools/ldml-const-builder.

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i'd put a script action in here for the generation, minor though

_Originally posted by @srl295 in https://github.com/keymanapp/keyman/pull/7113#discussion_r953986031_

In core/include/ldml/package.json