DAOS-19281 control: Suppress storage tier ratio warning for MD-on-SSD pools

[tanabarr]

Remove misleading low tier ratio warning when creating pools with
MD-on-SSD enabled. Low metadata-to-data ratios (~0.7%) are normal
and expected in MD-on-SSD mode, unlike PMem mode where <6% ratios
may impact performance. Add comprehensive unit tests.

Features: control

Steps for the author:

• Commit message follows the guidelines.
• Appropriate Features or Test-tag pragmas were used.
• Appropriate Functional Test Stages were run.
• At least two positive code reviews including at least one code owner from each category referenced in the PR.
• Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

• Gatekeeper requested (daos-gatekeeper added as a reviewer).

[github-actions]

Ticket title is 'Remove NOTICE: storage tier ratio is less than 1.00%, DAOS performance will suffer! during pool create under MDonSSD environment.'
Status is 'In Review'
Labels: '2.8.0rc1,md_on_ssd,test_2.8.0rc'
https://daosio.atlassian.net/browse/DAOS-19281

[daosbuild3]

Test stage Functional Hardware Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-18619/2/execution/node/1393/log

[knard38]

Mostly OK for me, just the warning message needs to be fixed and the copyright of the pool_test.go file needs to be updated.

[knard38]

The NOTICE: should be removed here as it will be already added from the caller of this function.

Suggested change

	return fmt.Sprintf("NOTICE: storage tier ratio is less than %0.2f%%, DAOS performance will suffer!", minPercentage)
	return fmt.Sprintf("storage tier ratio is less than %0.2f%%, DAOS performance will suffer!", minPercentage)

The unit test Test_checkPoolCreateTierRatioWarning() should also be updated accordingly.

[daosbuild3]

Test stage Unit Test completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18619/4/testReport/

[daosbuild3]

Test stage Functional Cluster Box Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-18619/5/execution/node/1662/log