(thunderbird) Add native ARM64 (win64-aarch64) support

[dennisameling]

⚠️ requires #2796 to be merged first.

Description

Use the shared Get-MozillaBuild / GetMozillaUrlFormats helpers (added with the Firefox ARM64 change) to select the native architecture build at install time.

• tools/chocolateyInstall.ps1: declare a per-package $builds map and resolve the build via the shared Get-MozillaBuild helper.
• update.ps1: emit Win64Arm64Format via the shared GetMozillaUrlFormats, pass it through both streams, and honor -Force/-IncludeStream (previously ignored).

Thunderbird ESR ships no arm64 build yet, so the arm64 entry stays dormant (empty checksum -> x64 fallback) and activates automatically once Mozilla publishes one. Depends on the Firefox ARM64 change for the shared helpers.

Motivation and Context

Companion PR to chocolatey/choco#3907 which aims to add native Windows arm64 support to Chocolatey.

How Has this Been Tested?

There's more detailed information in #2796, but even though Thunderbird doesn't have official arm64 support yet, the x64 installs just fine on an arm64 machine:

PS C:\repos\chocolatey-packages> choco install thunderbirdesr -s "C:\repos\chocolatey-packages\automatic\thunderbird" -f -y --allow-unofficial
Chocolatey v2.8.0-windowsarm-20260607-e77f2bec (DEBUG BUILD)

Chocolatey is not an official build (bypassed with --allow-unofficial).
 If you are seeing this message and it is not expected, your system may
 now be in a bad state. Only official builds are to be trusted.

Installing the following packages:
thunderbirdesr
By installing, you accept licenses for the packages.
thunderbirdesr v140.11.1 already installed. Forcing reinstall of version '140.11.1'.
 Please use upgrade if you meant to upgrade to a new version.
Downloading package from source 'C:\repos\chocolatey-packages\automatic\thunderbird'

thunderbirdesr v140.11.1 (forced)
thunderbirdesr package files install completed. Performing other installation steps.
Using locale 'en-US'...
Downloading thunderbirdesr
  from 'https://download.mozilla.org/?product=thunderbird-140.11.1esr&os=win64&lang=en-US'
Progress: 100% - Completed download of C:\Users\dennisameling\AppData\Local\Temp\chocolatey\thunderbirdesr\140.11.1\Thunderbird Setup 140.11.1esr.exe (71.31 MB).
Download of Thunderbird Setup 140.11.1esr.exe (71.31 MB) completed.
Hashes match.
Installing thunderbirdesr...
thunderbirdesr has been installed.
WARNING: No registry key found based on  'Mozilla Thunderbird'
  thunderbirdesr may be able to be automatically uninstalled.
 The install of thunderbirdesr was successful.
  Deployed to 'C:\Program Files\Mozilla Thunderbird'

Chocolatey installed 1/1 packages.
 See the log for details (C:\repos\choco\src\chocolatey.console\bin\Debug\net48\logs\chocolatey.log).
Exiting with 0

Screenshot (if appropriate, usually isn't needed):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Migrated package (a package has been migrated from another repository)

Checklist:

• My pull request is not coming from the master branch.
• My code follows the code style of this repository.
• My change requires a change to documentation (this usually means the notes in the description of a package).
• I have updated the documentation accordingly (this usually means the notes in the description of a package).
• I have updated the package description and it is less than 4000 characters.
• All files are up to date with the latest Contributing Guidelines
• The added/modified package passed install/uninstall in the Chocolatey Test Environment. Note that we don't support the use of any other environment.
• The changes only affect a single package (not including meta package).