Deprecate config-dir bring in certs-dir for TLS configuration

[harshavardhana]

Description

This PR is to provide an indication that config-dir will be removed
in future and all users should migrate to new --certs-dir option

Motivation and Context

Fixes #7016
Fixes #7032

Regression

No

How Has This Been Tested?

Start by testing the command line option by specifying new certs-dir location

minio server --certs-dir /tmp/my-certs ~/test

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added unit tests to cover my changes.
• I have added/updated functional tests in mint. (If yes, add mint PR # here: )
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #7033 into master will increase coverage by 0.02%.
The diff coverage is 14.81%.

@@            Coverage Diff            @@
##           master   #7033      +/-   ##
=========================================
+ Coverage   51.67%   51.7%   +0.02%     
=========================================
  Files         276     276              
  Lines       43585   43560      -25     
=========================================
- Hits        22524   22523       -1     
+ Misses      19049   19028      -21     
+ Partials     2012    2009       -3

Impacted Files	Coverage Δ
cmd/main.go	0% <ø> (-4.06%)	⬇️
cmd/server-main.go	10.23% <0%> (+0.14%)	⬆️
cmd/common-main.go	12.91% <0%> (-0.45%)	⬇️
cmd/gateway-main.go	15.84% <0%> (+0.23%)	⬆️
cmd/config-migrate.go	52.97% <100%> (ø)	⬆️
cmd/config-dir.go	40.74% <38.88%> (-2.12%)	⬇️
cmd/fs-v1.go	64.33% <0%> (+0.11%)	⬆️
cmd/fs-v1-helpers.go	68.8% <0%> (+0.61%)	⬆️
pkg/certs/certs.go	58.76% <0%> (+4.12%)	⬆️
cmd/disk-usage.go	100% <0%> (+5.26%)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fcb56d8...95822ec. Read the comment docs.

[harshavardhana]

PR updated @balamurugana @poornas - PTAL

[minio-ops]

Mint Automation

Test	Result
mint-tls.sh	✔️
mint-compression-xl.sh	✔️
mint-xl.sh	✔️
mint-gateway-nas.sh	✔️
mint-large-bucket.sh	✔️
mint-compression-fs.sh	✔️
mint-worm.sh	✔️
mint-fs.sh	✔️
mint-dist-xl.sh	✔️

[poornas]

LGTM