bug(MatTree): MatTree with interactive elements in each row is not keyboard accessible using a screenreader

#### Reproduction

Use StackBlitz to reproduce your issue:
- Components: https://angular-p4bmmy-zxpv6j.stackblitz.io

Steps to reproduce:
1. Navigate to StackBlitz link above on a Windows machine
2. Use the keyboard to interact with the tree by tabbing to a node, pressing enter or space to expand it, then tabbing to a nested checkbox and selecting it. Do not use the mouse.
3. Enable JAWS or NVDA screen reader
4. Attempt to repeat step 2, using the keyboard to interact with the tree
5. Manually expand the tree using the mouse then tab through the elements until you get to a nested checkbox. Press space or enter to select the checkbox.


#### Expected Behavior
Enabling a screen reader should not change the behavior when interacting with the tree using a keyboard. With a screen reader enabled, I should be able to expand a row, tab to a nested checkbox, and select the checkbox using only the keyboard.

#### Actual Behavior
Hitting space or enter appears to send the click event to the first encountered input element, rather than the focused element. In the linked example, this can be either the textbox above the tree or an unfocused checkbox, depending on how you tab through the list. Either way, the focused element doesn't seem to receive the event.

#### Environment

JAWS v2021.2102.34 / NVDA v2020.4 (reproducible with both)
Windows 10 Enterprise Version
Chrome Version 89.0.4389.114

Also tested with Firefox Version 87.0, but was not able to reproduce on FF

Inizia dalla riproduzione StackBlitz collegata e ripeti i passaggi usando solo la tastiera in Chrome su Windows con JAWS o NVDA. Confronta il comportamento con e senza lo screen reader, includendo la casella di controllo annidata e la casella di testo sopra l'albero. Il lavoro è completato quando l'elemento con il focus riceve Enter o Space e l'albero rimane accessibile da tastiera con uno screen reader, preservando il comportamento segnalato in Firefox.

Scritto dal modello di indicizzazione a partire dal testo della issue.