[9.x] Avoid throwing on invalid mime-type

[rodrigopedra]

league/flysystem version 3, changed to throw exceptions in places it previously returned null or false when a called method failed to execute.

As noted by issue #42758 , calling Illuminate\Filesystem\FilesystemAdapter@mimeType throws an exception when a file has a custom extension.

This becomes a problem when this method is called within other methods such in:

• framework/src/Illuminate/Filesystem/FilesystemAdapter.php

  Line 278 in 2bc1802

  'Content-Type' => $this->mimeType($path),

• framework/src/Illuminate/Mail/Attachment.php

  Line 98 in 2bc1802

  ->withMime($attachment->mime ?? $storage->mimeType($path));

• framework/src/Illuminate/Mail/Mailable.php

  Line 463 in 2bc1802

  array_merge(['mime' => $storage->mimeType($attachment['path'])], $attachment['options'])

Disclaimer: usage on Illuminate\Filesystem\FilesystemAdapter@response is changed to be lazily evaluated in PR #42760

This PR

• Changes Illuminate\Filesystem\FilesystemAdapter@mimeType to return false, as per its docblock, when the mime type cannot be detected
• Honors the throw configuration, when a developer sets it to true an exception will be thrown instead
• Adds two test cases covering both cases

EDIT

As league/flysystem changed the mime type detection behavior on tag 3.0.16, I updated the composer.json file to require at least this version.

Otherwise tests with prefer-lowest were failing