mgmt, fix generate.yml

[XiaofeiCao]

Description

This PR does:

1. Use macOS-13 for TypeSpec code generation. issue: https://github.com/Azure/azure-sdk-tools/issues/8368
2. Use parameters(instead of variables) for template compile-time expression. https://learn.microsoft.com/en-us/azure/devops/pipelines/process/variables?view=azure-devops&tabs=yaml%2Cbatch#understand-variable-syntax

   
   # ${{ <expression> }} is compile time template expression. 
   # For variables, it can only read its initial value, which is defined as
   variables:
   - var1
   value: initialValue

${{ variables.var1 }} # initialValue, not the value passed in

For parameters, it's template parameters and its value can be read in compile time

parameters:

• var1 default: value1 type: string

${{ parameters.var1 }} # if not passed in, value1, otherwise, it's passed in value

![image](https://github.com/Azure/azure-sdk-for-java/assets/92354331/6fed748c-cf21-4401-9ae9-08521f61d4d6)

3. Make `jobs` as root, instead of `steps` and move pool vmImage under job. This is due to pool vmImage condition can't happen at the root level.
https://stackoverflow.com/questions/63189744/execute-azure-devops-job-on-a-pool-based-on-conditional-parameter/76075535

Test:
1. Generate from Swagger
  a. pipeline: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=3898539&view=logs&j=42d88303-8e48-5332-e7e9-82bec1356e32&t=33740b31-17c1-53d0-4485-7f460d813a8f
  b. PR: https://github.com/Azure/azure-sdk-for-java/pull/40779
2. Generate from TypeSpec
  a. pipeline: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=3898538&view=logs&j=42d88303-8e48-5332-e7e9-82bec1356e32&t=ce7f9b1c-74d4-53cc-71fb-14221b7018a5
  b. PR: https://github.com/Azure/azure-sdk-for-java/pull/40780

Please add an informative description that covers that changes made by the pull request and link all relevant issues.

If an SDK is being regenerated based on a new swagger spec, a link to the pull request containing these swagger spec changes has been included above.

# All SDK Contribution checklist:
- [x] **The pull request does not introduce [breaking changes]**
- [ ] **CHANGELOG is updated for new features, bug fixes or other significant changes.**
- [ ] **I have read the [contribution guidelines](https://github.com/Azure/azure-sdk-for-java/blob/main/CONTRIBUTING.md).**

## [General Guidelines and Best Practices](https://github.com/Azure/azure-sdk-for-java/blob/main/CONTRIBUTING.md#developer-guide)
- [x] Title of the pull request is clear and informative.
- [x] There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, [see this page](https://github.com/Azure/azure-powershell/blob/master/documentation/development-docs/cleaning-up-commits.md).

### [Testing Guidelines](https://github.com/Azure/azure-sdk-for-java/blob/main/CONTRIBUTING.md#building-and-unit-testing)
- [x] Pull request includes test coverage for the included changes.

[XiaofeiCao]

curious that tsp-client can only run on mac?

I don't know why tsp-client in this pipeline will get permanent stuck on Windows/Linux... Ray hasn't met this issue, and I haven't seen major configuration differences either.

Use macOS for TypeSpec for now. Will switch if root cause is found.

[XiaofeiCao]

/check-enforcer override