2608 GitHub workflow updates [Rebase & FF]

[Michael Kubacki (makubacki)]

Description

Includes a few changes that need to be made in GitHub workflows after the 202608 branch transition.

---

.github: Update the Mu PR Validation workflow for 2608

Updates the branch trigger to release/202608 since it is on that
branch now.

---

.github: Only run Mu PR Validation on the default branch

The repo has moved the default branch from release/202511 to
release/202608. Mu Tiano Platforms only supports the latest branch
(2608). This skips the workflow anytime is not run on the default
branch in the future.

---

.github: Update the Release Draft workflow for 2608

Updates the branch trigger to release/202608 since it is on that
branch now.

---

• Impacts functionality?
• Impacts security?
• Breaking change?
• Includes tests?
• Includes documentation?

How This Was Tested

• Two commits are branch trigger updates without any change in the workflow itself.
• The change to detect the default branch and skip on other branches is already used in mu_plus (commit).

Integration Instructions

• N/A

[mu-automation]

✅ QEMU Validation Passed

Source Dependencies

Repository	Commit
mu_basecore	d7973b8
mu_tiano_platforms	82a93e0

Results

Platform	Target	Build	Boot	Overall Boot Time	Build Logs	Boot Logs
Q35	DEBUG	✅ success	✅ success	0m 21s	Build Logs	Boot Logs
ArmVirt	DEBUG	✅ success	✅ success	0m 17s	Build Logs	Boot Logs

Workflow run: https://github.com/microsoft/mu_basecore/actions/runs/36751688925

This comment was automatically generated by the Mu QEMU PR Validation workflow.

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (release/202608@095590b). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release/202608    #1947   +/-   ##
=================================================
  Coverage                  ?    1.86%           
=================================================
  Files                     ?     1674           
  Lines                     ?   423339           
  Branches                  ?     5159           
=================================================
  Hits                      ?     7878           
  Misses                    ?   415366           
  Partials                  ?       95           

Flag	Coverage Δ
FmpDevicePkg	9.63% <ø> (?)
MdeModulePkg	0.94% <ø> (?)
MdePkg	5.44% <ø> (?)
NetworkPkg	0.56% <ø> (?)
PolicyServicePkg	30.42% <ø> (?)
SecurityPkg	1.54% <ø> (?)
StandaloneMmPkg	0.50% <ø> (?)
UefiCpuPkg	4.71% <ø> (?)
UnitTestFrameworkPkg	11.72% <ø> (?)

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