chore: optimise function config.ConfigKeyToEnv

[mihir20]

Description

In a 1 hour profile config.ConfigKeyToEnv is taking near to 8.4minutes of execution, which can be seen from flame graph.

Internally this function is using regex which is we can be replaced and performance can be optimised. After replacing regex with simple for loops we can see improvements in the performance. attaching benchmark results here:

Old Code:  
BenchmarkConfigKeyToEnv-12    	 1287674	       922.6 ns/op	     265 B/op	      10 allocs/op
New Code: 
BenchmarkConfigKeyToEnv-12    	 9455137	       118.8 ns/op	      56 B/op	       3 allocs/op

Linear Ticket

https://linear.app/rudderstack/issue/PIPE-1103/optimise-function-configconfigkeytoenv-in-rudder-go-kit

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[fracasula]

LGTM, nice one 👍

The only difference I could spot is that your upper case function returns true for empty strings, but that was not the case with the old version.

It shouldn't be a problem though 👍

[Sidddddarth]

Good work!
Adding some more test cases around ConfigKeyToEnv would be nice.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.90%. Comparing base (bc95a3f) to head (3a9cb41).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #475      +/-   ##
==========================================
- Coverage   78.98%   78.90%   -0.08%     
==========================================
  Files          90       95       +5     
  Lines        6747     6793      +46     
==========================================
+ Hits         5329     5360      +31     
- Misses       1153     1160       +7     
- Partials      265      273       +8     

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