fix(analyzer): add unwanted channel drain before done channel returns for correct line count

[cx-artur-ribeiro]

Reason for Proposed Changes

• The analyzer's unwanted channel is buffered with capacity equal to the number of files. When all worker goroutines finish (wg.Wait()), the channels are closed and a done signal is sent. However, the computeValues() function uses a select statement that races between reading messages from unwanted and receiving the done signal.
• Once done is received, the function returned immediately, abandoning thousands of unread messages still sitting in the buffered unwanted channel. These lost exclusions meant the scan processed files that should have been excluded for huge projects.

Proposed Changes

• Drain the buffered unwanted channel before exiting;
• Update ListSupportedCloudProviders to match ListSupportedPlatforms() implementation, reducing tech dept and automatically fetch supported cloud providers from the constants;

I submit this contribution under the Apache-2.0 license.

[github-actions]

KICS version: v2.1.18

Category Results CRITICAL 0 HIGH 0 MEDIUM 0 LOW 0 INFO 0 TRACE 0 TOTAL 0	Metric Values Files scanned 1 Files parsed 1 Files failed to scan 0 Total executed queries 47 Queries failed to execute 0 Execution time 0

[cx-rui-araujo]

@cx-artur-ribeiro check my comment please

[cx-rui-araujo]

LGTM pal

[cx-eduardo-semanas]

LGTM