Merge #13823: qa: quote path in authproxy for external multiwallets

Summary:
fa67505e1ea007bdc081bc7425fb83d5455d8308 qa: Quote wallet name for rpc path (MarcoFalke)

Pull request description:

When using external multiwallets they are specified by their full path which might contain non-ascii characters (e.g. umlauts or emojis).

Fix this by url-quoting the path.

Tree-SHA512: 7cc66514579d9f602f88a6817c5ab43a44c6d3711df452dc904173f0bc34e2c0b2c34877497f06b61f6720c532fa183053f54622dc454e316c89cee7eaa72463

Backport of Core PR13823

Test Plan:

test_runner.py wallet*

In wallet_multiwallet.py change instances of w8 to ₿

test_runner.py wallet_multiwallet.py

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5187