[Prototype] Improve DDS stress testing: introduce enum stress mode

[clarenceli-msft]

AB#2729, AB#2730

This PR is a prototype for improving the Test - DDS Stress line by using a numeric stressLevel instead of a boolean isStress. This change allows for more granular control over whether to use stress runs and to what degree.

The follow-up tasks include:

1. Integrating this functionality (potentially as a stage) into the CI build pipeline with a light stress level mode, so it can be triggered in the PR gateway.

2. Creating a long-running pipeline to execute the DDS stress tests with a heavy stress level mode, scheduled to run periodically during off-peak hours, similar to the test stability pipeline.

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List any specific things you want to get reviewer opinions on, and anything a reviewer would need to know to review this PR effectively.
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[msfluid-bot]

⯅ @fluid-example/bundle-size-tests: +245 Bytes

Metric Name	Baseline Size	Compare Size	Size Diff
aqueduct.js	457.54 KB	457.58 KB	⯅ +35 Bytes
azureClient.js	555.3 KB	555.35 KB	⯅ +49 Bytes
connectionState.js	680 Bytes	680 Bytes	■ No change
containerRuntime.js	258.68 KB	258.7 KB	⯅ +14 Bytes
fluidFramework.js	391.52 KB	391.53 KB	⯅ +14 Bytes
loader.js	134.07 KB	134.08 KB	⯅ +14 Bytes
map.js	42.12 KB	42.12 KB	⯅ +7 Bytes
matrix.js	145.63 KB	145.63 KB	⯅ +7 Bytes
odspClient.js	523.08 KB	523.13 KB	⯅ +49 Bytes
odspDriver.js	97.17 KB	97.19 KB	⯅ +21 Bytes
odspPrefetchSnapshot.js	42.27 KB	42.29 KB	⯅ +14 Bytes
sharedString.js	162.64 KB	162.65 KB	⯅ +7 Bytes
sharedTree.js	382.03 KB	382.04 KB	⯅ +7 Bytes
Total Size	3.27 MB	3.27 MB	⯅ +245 Bytes

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Baseline commit: 957b194

Generated by 🚫 dangerJS against c6d935a

[Abe27342]

Rather than make this numeric, I'd prefer we use an enum or string union with well-defined semantics for its members. Ideally a test author should be able to look at the docs here and make informed decisions on how to write their tests. The semantics should be in terms of the expectations for

• roughly how long should the tests take?
• are the tests expected to be evergreen? (true for deterministic seeds, false for random seeds)

in addition to other criteria you might find relevant. Because this doc is FF internal, I think it's fine if the documentation for those modes mentions the strategy we use for running tests in that mode (e.g. if we go with the strategies we discussed, we document here that a 'short' mode is run on all CI runs as part of the package's normal correctness tests, a 'medium' is run post check-in when a package is changed, and a 'long' is run on a fixed schedule using random seeds)

[Abe27342]

all the other changes in this PR look fine at a glance, I can review in more detail for places where there are missing changes of a similar sort (if any) and/or nitpick. but it generally looks like what I expected.

[clarenceli-msft]

I have updated the PR and included the unit tests for introducing enum stress modes. For some tests, like optionalChangeRebaser.test.ts, parameters such as numberOfEditsToRebaseOver should be customized by the area expert or owner, depending on the stress mode. Currently, I prefer to leave these parameters as they are, so they will only differ when stress mode is enabled as before.