fix: use repo-root-relative paths in Swift podspec

[thomson-t]

Summary

• Fixes pod trunk push failure for mParticle-Apple-SDK-Swift by moving the podspec from mParticle-Apple-SDK-Swift/ subdirectory to the repo root (alongside the other two podspecs).
• source_files changed from Sources/**/*.swift to mParticle-Apple-SDK-Swift/Sources/**/*.swift
• license file changed from ../LICENSE to LICENSE
• Updated all workflow, doc, and CI references to the new path.

Context

CocoaPods resolves paths in a podspec relative to the repo root (defined by s.source) during pod trunk push, but relative to the podspec file's directory during pod lib lint. With the podspec in a subdirectory, these two tools are fundamentally incompatible -- any path that works for one breaks the other.

Moving the podspec to the repo root eliminates this mismatch. Both pod lib lint and pod trunk push now resolve paths from the same location.

This was the first pod trunk push for this pod (CI step added in #723), so the bug was latent since the podspec was created.

Failed run: https://github.com/mParticle/mparticle-apple-sdk/actions/runs/24206575157/job/70669365797

Test plan

• pod lib lint mParticle-Apple-SDK-Swift.podspec --allow-warnings passes locally
• build-and-lint / pod-lint CI job passes
• All kit Pod Lint jobs pass
• Full CI green on PR

[cursor]

PR Summary

Medium Risk
Touches CocoaPods publishing and CI/release workflows; low code risk but could break pod lib lint/pod trunk push if paths are still incorrect or assumptions differ across runners.

Overview
Fixes mParticle-Apple-SDK-Swift.podspec to work when CocoaPods evaluates paths from the repo root (not the podspec’s directory) by updating s.source_files and the LICENSE path.

Updates CI/release workflows and docs to reference the Swift podspec at the repo root (removing the mParticle-Apple-SDK-Swift/mParticle-Apple-SDK-Swift.podspec path) for pod lib lint, version bumping, and pod trunk push.

^{Reviewed by Cursor Bugbot for commit 865a856. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

📦 SDK Size Impact Report

Measures how much the SDK adds to an app's size (with-SDK minus without-SDK).

Metric	Target Branch	This PR	Change
App Bundle Impact	1.75 MB	1.75 MB	-4 KB
Executable Impact	848 bytes	848 bytes	+N/A
XCFramework Size	6.38 MB	6.38 MB	-4 KB

➡️ SDK size impact change is minimal.

Raw measurements

Target branch (main):

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1880,"with_sdk_executable_size_bytes":76312,"sdk_impact_kb":1796,"sdk_executable_impact_bytes":848,"xcframework_size_kb":6532}

This PR:

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1876,"with_sdk_executable_size_bytes":76312,"sdk_impact_kb":1792,"sdk_executable_impact_bytes":848,"xcframework_size_kb":6528}