Error parsing email attachment name

**Describe the bug**
I found a problem parsing the name of an email attachment. If I open the same email in outlook or thunderbird the attachment name is shown correctly. Also tested with an RFC 2047 decoder and works OK.

**To Reproduce**
Send an email with an attachment whose name is encoded in the following way:

```
Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;
name="=?iso-8859-1?Q?Preparaci=F3n_de_puesto_de_trabajo_Sofia_Cafaro_-_Altenix_?=
=?iso-8859-1?Q?BC.lsx?="
Content-Description:
=?iso-8859-1?Q?Preparaci=F3n_de_puesto_de_trabajo_Sofia_Cafaro_-_Altenix_?=
=?iso-8859-1?Q?BC.xlsx?=
Content-Disposition: attachment;
filename="=?iso-8859-1?Q?Preparaci=F3n_de_puesto_de_trabajo_Sofia_Cafaro_-_Altenix_?=
=?iso-8859-1?Q?BC.xlsx?="; size=69949;
creation-date="Tue, 19 Oct 2021 18:50:44 GMT";
modification-date="Tue, 19 Oct 2021 18:50:44 GMT"
Content-Transfer-Encoding: base64
```

**Expected behavior**
The attachment name should be `Preparación de puesto de trabajo Sofia Cafaro - Altenix BC.xlsx` but the api shows it as `=?iso-8859-1?Q?Preparaci=F3n_de_puesto_de_trabajo_Sofia_Cafaro_-_Altenix_?= =?iso-8859-1?Q?BC.xlsx?=`

**Version tested:**
- 1.6.7
- Java 8
- CentOS Linux release 7.7.1908

**Mail server:**
- Protocol being used: IMAP
- Vendor/product: The email was generated by microsoft outlook

Start by reproducing the reported IMAP message with the supplied MIME headers and compare the API's attachment-name result with the RFC 2047 decoder output. Trace the Java mail API's attachment filename parsing entry point; done means the expected decoded filename is returned for this sample and the case is covered by a regression test.

Written by the indexing model from the issue text.