… part 2

part 2 of 4531
Replace the last pexpect with os.execvp / bash session script to improve picocom performance

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#### What I did
added the second part of the change to streamline the picocom launch process
#### How I did it
replaced the second pexpect call with execvp
#### How to verify it
first, launch console app just like before
then, use ps -ef to make sure "connect line" is no longer a standalone process
#### New command output (if the output of a command-line utility has changed)
connect line X or just reverse ssh

#### Which release branch to backport (provide reason below if selected)

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- Note we only backport fixes to a release branch, *not* features!
- Please also provide a reason for the backporting below.
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- [x] 202006
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- [ ] 202305
- [ ] 202311
- [ ] 202405
- [ ] 202411
- [ ] 202505
- [x] 202603
- [x] 202605

Signed-off-by: Sonic Build Admin <sonicbld@microsoft.com>