workflows: add TailscaleKit tests to CI

[barnstar]

updates tailscale/tailscale#15802

Updates the tests to run using go 1.24 and
adds a CI run to build the swift/TailscaleKit
targets and tests.

[ghost]

Pull Request Revisions

Revision	Description
r6	Modified Swift workflow and Makefile Updated GitHub Actions workflow to add iOS and macOS build steps, and modified Makefile test target to separate build and test phases
r5	Added test control make command Modified test target to run make all in tstestcontrol directory before other test preparations
r4	Updated libtstestcontrol library reference Modified the library reference for libtstestcontrol.a in the Xcode project, updating its path and framework inclusion
r3	Removed test host project files Deleted entire TailscaleKitTestHost directory and related target configurations from Xcode project
r2	Updated macOS and Go versions Updated GitHub workflow to use macOS-15 and Go 1.24 for Swift project testing
r1	Added Swift project GitHub Actions workflow Created a new GitHub Actions workflow for Swift project testing on macOS, using Go 1.21 and running tests from the swift directory

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☑️ AI review skipped for r6

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