Fix missing footer space during WiFi provisioning (#4868)
Fix missing footer space during WiFi provisioning (#4868)

As of a8681876 ("Reduce use of maximum-sized packet buffers (#4434)"),
network provisioning does not allocate enough space to encrypt the WiFi
credentials payload, resulting in the following error:

 CHIP:NP: Failed in sending Network Creds. error Error 4047 (0x00000FCF)

Pending API improvements to make these errors less likely, manually add
the needed extra space at allocation time.

Fixes #4823
project-chip/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip