fix(bridges): obfuscate the password in bridges API responses

[lafirest]

port redact from 4.3 to master, and obfuscate sensitive data in the response when querying bridges information by API
fix EMQX-8374

[coveralls]

Pull Request Test Coverage Report for Build 3780093577

• 87 of 95 (91.58%) changed or added relevant lines in 3 files are covered.
• 30 unchanged lines in 14 files lost coverage.
• Overall coverage increased (+0.05%) to 79.624%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/emqx/src/emqx_map_lib.erl	8	9	88.89%
apps/emqx/src/emqx_misc.erl	61	64	95.31%
apps/emqx_bridge/src/emqx_bridge_api.erl	18	22	81.82%

Files with Coverage Reduction	New Missed Lines	%
apps/emqx_conf/src/emqx_conf_schema.erl	1	92.31%
apps/emqx_gateway/src/mqttsn/emqx_sn_channel.erl	1	73.04%
apps/emqx_management/src/emqx_mgmt_api_trace.erl	1	86.49%
apps/emqx_resource/src/emqx_resource_worker.erl	1	84.91%
apps/emqx/src/emqx_authentication_config.erl	1	83.62%
apps/emqx/src/emqx_flapping.erl	1	85.11%
apps/emqx/src/emqx_limiter/src/emqx_limiter_schema.erl	1	85.92%
apps/emqx/src/emqx_logger.erl	1	80.49%
apps/emqx/src/emqx_session.erl	1	87.6%
apps/emqx/src/emqx_banned.erl	2	89.39%

Totals
Change from base Build 3766676825:	0.05%
Covered Lines:	22626
Relevant Lines:	28416

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💛 - Coveralls

[zmstone]

I'm afraid the situation is a bit more complicated than what it seems to be.
Since the GET response is used for dashboard to pre-fill the text boxes so the user can update some fields and click the "Save" or "Update" button to update bridge configuration, we'll need to handle the case in which the sensitive filed is provided with value <<"******">> then we do not update the password for this config.

Otherwise for whatever they want to update, they will have to re-fill the password box.
super inconvenient, but also not making it more secure than before because the user
would likely have to copy-paste the password over and over again, i.e. actually higher chance to leak it.

resolved